{"id":"CVE-2026-34987","aliases":["DEBIAN-CVE-2026-34987","EUVD-2026-21031","GHSA-xx5w-cvp6-jv83","JLSEC-2026-1361","RUSTSEC-2026-0095","SUSE-SU-2026:21789-1","UBUNTU-CVE-2026-34987","openSUSE-SU-2026:20749-1"],"status":"published","title":"Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","severity":{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00283,"percentile":0.21035,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-125","CWE-787"],"published":"2026-04-09T12:00:00Z","modified":"2026-11-04T20:03:05Z","fixes":[{"ecosystem":"crates.io","package":"wasmtime","fixed_in":["36.0.7","42.0.2","43.0.1"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:14","package":"rust-wasmtime","fixed_in":["36.0.7+dfsg-1"],"sources":["osv"]},{"ecosystem":"Julia","package":"Wasmtime_jll","fixed_in":["45.0.1+0"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"crates.io","package":"wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"25.0.0"},{"fixed":"36.0.7"}]}]},{"source":"ghsa","ecosystem":"crates.io","package":"wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"37.0.0"},{"fixed":"42.0.2"}]}]},{"source":"ghsa","ecosystem":"crates.io","package":"wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"43.0.0"},{"last_affected":"43.0.0"},{"fixed":"43.0.1"}]}],"versions":["43.0.0"]},{"source":"osv","ecosystem":"Debian:13","package":"rust-wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["26.0.1+dfsg-10","26.0.1+dfsg-3","26.0.1+dfsg-4","26.0.1+dfsg-5","26.0.1+dfsg-6","26.0.1+dfsg-7","26.0.1+dfsg-8","26.0.1+dfsg-9","27.0.0+dfsg-2","27.0.0+dfsg-3","27.0.0+dfsg-4","28.0.1+dfsg-1","28.0.1+dfsg-2","28.0.1+dfsg-3","29.0.1+dfsg-1","29.0.1+dfsg-2","29.0.1+dfsg-3","29.0.1+dfsg-4","29.0.1+dfsg-5","29.0.1+dfsg-6","29.0.1+dfsg-7","29.0.1+dfsg-8","36.0.11+dfsg-1","36.0.12+dfsg-1","36.0.12+dfsg-2","36.0.12+dfsg-3","36.0.13+dfsg-1","36.0.5+dfsg-1","36.0.5+dfsg-2","36.0.5+dfsg-3","36.0.5+dfsg-4","36.0.5+dfsg-5","36.0.6+dfsg-1","36.0.6+dfsg-2","36.0.6+dfsg-3","36.0.6+dfsg-4","36.0.6+dfsg-5","36.0.6+dfsg-6","36.0.6+dfsg-7","36.0.7+dfsg-1","36.0.8+dfsg-1","36.0.9+dfsg-1","36.0.9+dfsg-2"]},{"source":"osv","ecosystem":"Debian:14","package":"rust-wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"36.0.7+dfsg-1"}]}],"versions":["26.0.1+dfsg-10","26.0.1+dfsg-3","26.0.1+dfsg-4","26.0.1+dfsg-5","26.0.1+dfsg-6","26.0.1+dfsg-7","26.0.1+dfsg-8","26.0.1+dfsg-9","27.0.0+dfsg-2","27.0.0+dfsg-3","27.0.0+dfsg-4","28.0.1+dfsg-1","28.0.1+dfsg-2","28.0.1+dfsg-3","29.0.1+dfsg-1","29.0.1+dfsg-2","29.0.1+dfsg-3","29.0.1+dfsg-4","29.0.1+dfsg-5","29.0.1+dfsg-6","29.0.1+dfsg-7","29.0.1+dfsg-8","36.0.5+dfsg-1","36.0.5+dfsg-2","36.0.5+dfsg-3","36.0.5+dfsg-4","36.0.5+dfsg-5","36.0.6+dfsg-1","36.0.6+dfsg-2","36.0.6+dfsg-3","36.0.6+dfsg-4","36.0.6+dfsg-5","36.0.6+dfsg-6","36.0.6+dfsg-7"]},{"source":"osv","ecosystem":"crates.io","package":"wasmtime","ranges":[{"type":"SEMVER","events":[{"introduced":"25.0.0"},{"fixed":"36.0.7"}]}]},{"source":"osv","ecosystem":"crates.io","package":"wasmtime","ranges":[{"type":"SEMVER","events":[{"introduced":"37.0.0"},{"fixed":"42.0.2"}]}]},{"source":"osv","ecosystem":"crates.io","package":"wasmtime","ranges":[{"type":"SEMVER","events":[{"introduced":"43.0.0"},{"fixed":"43.0.1"}]}],"versions":["43.0.0"]},{"source":"osv","ecosystem":"Julia","package":"Wasmtime_jll","ranges":[{"type":"SEMVER","events":[{"introduced":"39.0.0+0"},{"fixed":"45.0.1+0"}]}]},{"source":"osv","ecosystem":"crates.io","package":"wasmtime","ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-0"},{"fixed":"36.0.7"},{"introduced":"37.0.0"},{"fixed":"42.0.2"},{"introduced":"43.0.0"},{"fixed":"43.0.1"}]}]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"rust-wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["26.0.1+dfsg-3"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"rust-wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["36.0.5+dfsg-1","36.0.13+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"rust-wasmtime","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["26.0.1+dfsg-3","26.0.1+dfsg-4","28.0.1+dfsg-3","29.0.1+dfsg-5","36.0.5+dfsg-1"]}],"products":[{"vendor":"bytecodealliance","product":"wasmtime"}],"references":[{"url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83","tags":["x_refsource_CONFIRM","Vendor Advisory","advisory","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34987","tags":["advisory","web"]},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0095.html","tags":["web","advisory"]},{"url":"https://github.com/advisories/GHSA-xx5w-cvp6-jv83","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34987.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-34987","tags":["advisory"]},{"url":"https://github.com/bytecodealliance/wasmtime","tags":["package"]},{"url":"https://crates.io/crates/wasmtime","tags":["package"]},{"url":"https://github.com/bytecodealliance/wasmtime/pull/13014","tags":["web"]},{"url":"https://www.suse.com/support/update/announcement/2026/suse-su-202621789-1/","tags":["advisory"]},{"url":"https://bugzilla.suse.com/1259205","tags":["report"]},{"url":"https://bugzilla.suse.com/1261839","tags":["report"]},{"url":"https://bugzilla.suse.com/1261871","tags":["report"]},{"url":"https://bugzilla.suse.com/1261894","tags":["report"]},{"url":"https://bugzilla.suse.com/1261954","tags":["report"]},{"url":"https://bugzilla.suse.com/1261963","tags":["report"]},{"url":"https://bugzilla.suse.com/1261968","tags":["report"]},{"url":"https://bugzilla.suse.com/1261974","tags":["report"]},{"url":"https://bugzilla.suse.com/1262007","tags":["report"]},{"url":"https://bugzilla.suse.com/1262032","tags":["report"]},{"url":"https://bugzilla.suse.com/1262036","tags":["report"]},{"url":"https://bugzilla.suse.com/1262040","tags":["report"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34941","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34942","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34943","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34944","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34945","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34946","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34987","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-34988","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-35186","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-35195","tags":["web"]},{"url":"https://ubuntu.com/security/CVE-2026-34987","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-34987","tags":["report"]},{"url":"","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-34987","title":"Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","status":"published","published":"2026-04-09T18:48:33.552Z","modified":"2026-04-10T14:12:55.374Z","cvss":[{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical","assessor":"cna"}],"cwes":["CWE-125","CWE-787"],"updated_at":"2026-11-02T14:20:14.665567Z"}],"euvd":[{"id":"EUVD-2026-21031","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","status":"published","published":"2026-04-09T18:48:33Z","modified":"2026-04-10T14:12:55Z","cvss":[{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"updated_at":"2026-11-02T19:24:29.850635Z"}],"ghsa":[{"id":"GHSA-xx5w-cvp6-jv83","title":"Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access","description":"### Impact\n\nWasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox.\n\nThis vulnerability requires use of the Winch compiler (`-Ccompiler=winch`). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice.\n\nThis Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE.\n\n### Patches\n\nWasmtime 43.0.1, 42.0.2, and 36.0.7 have been released with fixes for this issue.\n\n### Workaround\n\nThere are no workarounds within the Winch compiler backend while using the affected versions. Users of Wasmtime are encouraged either to upgrade to patched versions or, if that is not possible, use the Cranelift compiler backend.","status":"published","published":"2026-04-10T15:31:18Z","modified":"2026-04-10T15:31:20Z","cvss":[{"version":"4.0","score":9.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","level":"critical"}],"cwes":["CWE-125","CWE-787"],"updated_at":"2026-11-02T14:39:52.102227Z"}],"nvd":[{"id":"CVE-2026-34987","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","status":"published","published":"2026-04-09T19:16:25Z","modified":"2026-10-26T22:10:00.163Z","cvss":[{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"},{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"primary"}],"cwes":["CWE-125","CWE-787"],"updated_at":"2026-11-02T14:12:13.902911Z"}],"osv":[{"id":"CVE-2026-34987","title":"Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","status":"published","published":"2026-04-09T18:48:33.552Z","modified":"2026-10-28T02:30:42.918433436Z","cvss":[{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-125","CWE-787"],"updated_at":"2026-11-02T15:45:02.673625Z"},{"id":"DEBIAN-CVE-2026-34987","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","status":"published","published":"2026-04-09T19:16:25Z","modified":"2026-10-27T09:47:41.919712701Z","cvss":[{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:45:54.587575Z"},{"id":"GHSA-xx5w-cvp6-jv83","title":"Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access","description":"### Impact\n\nWasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox.\n\nThis vulnerability requires use of the Winch compiler (`-Ccompiler=winch`). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice.\n\nThis Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE.\n\n### Patches\n\nWasmtime 43.0.1, 42.0.2, and 36.0.7 have been released with fixes for this issue.\n\n### Workaround\n\nThere are no workarounds within the Winch compiler backend while using the affected versions. Users of Wasmtime are encouraged either to upgrade to patched versions or, if that is not possible, use the Cranelift compiler backend.","status":"published","published":"2026-04-10T15:31:18Z","modified":"2026-09-10T03:51:04.079605148Z","cvss":[{"version":"4.0","score":9.2,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","level":"critical"}],"cwes":["CWE-125","CWE-787"],"updated_at":"2026-11-02T15:47:00.604718Z"},{"id":"JLSEC-2026-1361","title":"Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access","description":"### Impact\n\nWasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox.\n\nThis vulnerability requires use of the Winch compiler (`-Ccompiler=winch`). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice.\n\nThis Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE.\n\n### Patches\n\nWasmtime 43.0.1, 42.0.2, and 36.0.7 have been released with fixes for this issue.\n\n### Workaround\n\nThere are no workarounds within the Winch compiler backend while using the affected versions. Users of Wasmtime are encouraged either to upgrade to patched versions or, if that is not possible, use the Cranelift compiler backend.","status":"published","published":"2026-08-21T20:43:33.133Z","modified":"2026-08-21T21:14:21.072331839Z","cvss":[{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"},{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical"}],"updated_at":"2026-11-02T15:47:18.159338Z"},{"id":"RUSTSEC-2026-0095","title":"Wasmtime with Winch compiler backend may allow a sandbox-escaping memory access","description":"This is an entry in the RustSec database for the Wasmtime security advisory\nlocated at\nhttps://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83\nFor more information see the GitHub-hosted security advisory.","status":"published","published":"2026-04-09T12:00:00Z","modified":"2026-10-12T18:00:08.330233116Z","cvss":[{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"updated_at":"2026-11-02T15:53:40.430679Z"},{"id":"UBUNTU-CVE-2026-34987","description":"Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","status":"published","published":"2026-04-09T19:16:00Z","modified":"2026-11-04T20:03:05.336543844Z","cvss":[{"version":"4.0","score":9,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"},{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-04T21:44:40.383812Z"},{"id":"openSUSE-SU-2026:20749-1","title":"Security update for tree-sitter","description":"This update for tree-sitter fixes the following issues\n\nSecurity issues:\n\n- CVE-2026-34941: wasmtime: crafted input string can lead to an out-of-bound read (bsc#1261871).\n- CVE-2026-34942: wasmtime: unaligned pointers can lead to a denial of service (bsc#1261894).\n- CVE-2026-34943: wasmtime: lifting `flags` component value can lead to a denial of service (bsc#1261954).\n- CVE-2026-34944: wasmtime: out-of-bounds read during WebAssembly compilation can lead to a denial of service\n  (bsc#1261963).\n- CVE-2026-34945: wasmtime: incorrectly translated table.size could lead to disclosing data (bsc#1262007).\n- CVE-2026-34946: wasmtime: denial of service due to WebAssembly compilation error (bsc#1261974).\n- CVE-2026-34987: wasmtime: winch compiler backend may allow a sandbox-escaping memory access (bsc#1262032).\n- CVE-2026-34988: wasmtime: pooling allocator instances can cause data leakage (bsc#1261968).\n- CVE-2026-35186: wasmtime: translating the table.grow operator can cause a masked return value (bsc#1262036).\n- CVE-2026-35195: wasmtime: transcoding strings can lead to an out of bound write or a crash (bsc#1262040).\n\nChanges for tree-sitter:\n\n- update to 0.26.8:\n\n * fix(generate): allow disabling qjs-rt feature from CLI by @WillLillis in\n #5448\n * fix(lib): document invariants that must be upheld for TSInputEdit by\n @WillLillis in #5452\n * fix(cli): correct typo in parse command's help text by @WillLillis in #5465\n * perf(cli): misc. improvements by @tree-sitter-ci-bot[bot] in #5476\n * Fix wasm loading of languages w/ multiple reserved word sets by\n @tree-sitter-ci-bot[bot] in #5477\n * generate: avoid panicking when a supertype only has hidden external token\n children by @tree-sitter-ci-bot[bot] in #5478\n","status":"published","published":"2026-05-14T08:07:53Z","modified":"2026-05-19T18:23:48.124613698Z","updated_at":"2026-11-02T16:58:41.463445Z"},{"id":"SUSE-SU-2026:21789-1","title":"Security update for tree-sitter","description":"This update for tree-sitter fixes the following issues\n\nSecurity issues:\n\n- CVE-2026-34941: wasmtime: crafted input string can lead to an out-of-bound read (bsc#1261871).\n- CVE-2026-34942: wasmtime: unaligned pointers can lead to a denial of service (bsc#1261894).\n- CVE-2026-34943: wasmtime: lifting `flags` component value can lead to a denial of service (bsc#1261954).\n- CVE-2026-34944: wasmtime: out-of-bounds read during WebAssembly compilation can lead to a denial of service\n  (bsc#1261963).\n- CVE-2026-34945: wasmtime: incorrectly translated table.size could lead to disclosing data (bsc#1262007).\n- CVE-2026-34946: wasmtime: denial of service due to WebAssembly compilation error (bsc#1261974).\n- CVE-2026-34987: wasmtime: winch compiler backend may allow a sandbox-escaping memory access (bsc#1262032).\n- CVE-2026-34988: wasmtime: pooling allocator instances can cause data leakage (bsc#1261968).\n- CVE-2026-35186: wasmtime: translating the table.grow operator can cause a masked return value (bsc#1262036).\n- CVE-2026-35195: wasmtime: transcoding strings can lead to an out of bound write or a crash (bsc#1262040).\n\nChanges for tree-sitter:\n\n- update to 0.26.8:\n\n * fix(generate): allow disabling qjs-rt feature from CLI by @WillLillis in\n #5448\n * fix(lib): document invariants that must be upheld for TSInputEdit by\n @WillLillis in #5452\n * fix(cli): correct typo in parse command's help text by @WillLillis in #5465\n * perf(cli): misc. improvements by @tree-sitter-ci-bot[bot] in #5476\n * Fix wasm loading of languages w/ multiple reserved word sets by\n @tree-sitter-ci-bot[bot] in #5477\n * generate: avoid panicking when a supertype only has hidden external token\n children by @tree-sitter-ci-bot[bot] in #5478\n","status":"published","published":"2026-05-14T08:09:11Z","modified":"2026-05-28T18:24:08.686123956Z","updated_at":"2026-11-02T15:54:02.654057Z"}]}}