{"id":"CVE-2026-63476","aliases":["EUVD-2026-116272","GHSA-9x82-4j54-863h"],"status":"published","title":"isomorphic-git: Unbounded memory allocation from attacker-controlled delta target size (DoS)","description":"isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git reads a server-controlled targetSize while applying a packfile delta in src/utils/applyDelta.js and passes it without a bound to Buffer.alloc(targetSize). A malicious or man-in-the-middle-controlled remote can send one delta header that causes git.clone() or git.fetch() to allocate approximately 2 GB before validating the actual delta output. GitPackIndex.fromPack swallows the later size-mismatch error, so a host with sufficient memory may retain the resource waste without a visible failure, while containers, serverless functions, and small virtual machines may terminate. Node.js heap limits do not mitigate the off-heap Buffer allocation. This issue is fixed in version 1.38.6.","severity":{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00285,"percentile":0.21322,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-400","CWE-789"],"published":"2026-11-03T19:44:06Z","modified":"2026-11-07T03:27:39Z","products":[{"vendor":"isomorphic-git","product":"isomorphic-git"}],"references":[{"url":"https://github.com/isomorphic-git/isomorphic-git/security/advisories/GHSA-9x82-4j54-863h","tags":["x_refsource_CONFIRM","exploit","advisory"]},{"url":"https://github.com/isomorphic-git/isomorphic-git/pull/2370","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/isomorphic-git/isomorphic-git/commit/823843d1cd19182df79bc907c767f5bcecb39a0b","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/isomorphic-git/isomorphic-git/releases/tag/v1.38.6","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63476.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63476","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-63476","title":"isomorphic-git: Unbounded memory allocation from attacker-controlled delta target size (DoS)","description":"isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git reads a server-controlled targetSize while applying a packfile delta in src/utils/applyDelta.js and passes it without a bound to Buffer.alloc(targetSize). A malicious or man-in-the-middle-controlled remote can send one delta header that causes git.clone() or git.fetch() to allocate approximately 2 GB before validating the actual delta output. GitPackIndex.fromPack swallows the later size-mismatch error, so a host with sufficient memory may retain the resource waste without a visible failure, while containers, serverless functions, and small virtual machines may terminate. Node.js heap limits do not mitigate the off-heap Buffer allocation. This issue is fixed in version 1.38.6.","status":"published","published":"2026-11-03T19:44:06.908Z","modified":"2026-11-07T03:27:39.077Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna"}],"cwes":["CWE-400","CWE-789"],"updated_at":"2026-11-07T04:32:31.343254Z"}],"euvd":[{"id":"EUVD-2026-116272","description":"isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git reads a server-controlled targetSize while applying a packfile delta in src/utils/applyDelta.js and passes it without a bound to Buffer.alloc(targetSize). A malicious or man-in-the-middle-controlled remote can send one delta header that causes git.clone() or git.fetch() to allocate approximately 2 GB before validating the actual delta output. GitPackIndex.fromPack swallows the later size-mismatch error, so a host with sufficient memory may retain the resource waste without a visible failure, while containers, serverless functions, and small virtual machines may terminate. Node.js heap limits do not mitigate the off-heap Buffer allocation. This issue is fixed in version 1.38.6.","status":"published","published":"2026-11-03T19:44:06Z","modified":"2026-11-07T03:27:39Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-07T04:08:16.282099Z"}],"nvd":[{"id":"CVE-2026-63476","description":"isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git reads a server-controlled targetSize while applying a packfile delta in src/utils/applyDelta.js and passes it without a bound to Buffer.alloc(targetSize). A malicious or man-in-the-middle-controlled remote can send one delta header that causes git.clone() or git.fetch() to allocate approximately 2 GB before validating the actual delta output. GitPackIndex.fromPack swallows the later size-mismatch error, so a host with sufficient memory may retain the resource waste without a visible failure, while containers, serverless functions, and small virtual machines may terminate. Node.js heap limits do not mitigate the off-heap Buffer allocation. This issue is fixed in version 1.38.6.","status":"published","published":"2026-11-03T20:18:16.063Z","modified":"2026-11-07T04:17:32.99Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","level":"medium","assessor":"secondary"}],"cwes":["CWE-400","CWE-789"],"updated_at":"2026-11-07T07:04:25.467195Z"}],"osv":[{"id":"CVE-2026-63476","title":"isomorphic-git: Unbounded memory allocation from attacker-controlled delta target size (DoS)","description":"isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git reads a server-controlled targetSize while applying a packfile delta in src/utils/applyDelta.js and passes it without a bound to Buffer.alloc(targetSize). A malicious or man-in-the-middle-controlled remote can send one delta header that causes git.clone() or git.fetch() to allocate approximately 2 GB before validating the actual delta output. GitPackIndex.fromPack swallows the later size-mismatch error, so a host with sufficient memory may retain the resource waste without a visible failure, while containers, serverless functions, and small virtual machines may terminate. Node.js heap limits do not mitigate the off-heap Buffer allocation. This issue is fixed in version 1.38.6.","status":"published","published":"2026-11-03T19:44:06.908Z","modified":"2026-11-08T02:31:00.688983693Z","cvss":[{"version":"3.1","score":4.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-400","CWE-789"],"updated_at":"2026-11-08T02:57:53.255434Z"}]}}