{"id":"CVE-2026-5503","aliases":["ALPINE-CVE-2026-5503","DEBIAN-CVE-2026-5503","EUVD-2026-21234","GHSA-65xm-pfx9-g5p3","JLSEC-2026-731","UBUNTU-CVE-2026-5503"],"status":"published","title":"out-of-bounds write in TLSX_EchChangeSNI via attacker-controlled publicName","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","severity":{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.0053,"percentile":0.45078,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-787"],"published":"2026-04-09T22:35:39Z","modified":"2026-11-03T06:33:06Z","fixes":[{"ecosystem":"Alpine:v3.23","package":"wolfssl","fixed_in":["5.9.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.24","package":"wolfssl","fixed_in":["5.9.1-r0"],"sources":["osv"]},{"ecosystem":"Julia","package":"wolfSSL_jll","fixed_in":["5.9.2+0"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Alpine:v3.23","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.9.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.24","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.9.1-r0"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.5.4-2","5.5.4-2+deb12u1","5.5.4-2+deb12u2","5.5.4-2+deb12u3","5.5.4-2.1","5.6.4-1","5.6.4-2","5.6.6-1","5.6.6-1.1","5.6.6-1.2","5.6.6-1.3","5.6.6-1.3~exp1","5.7.0-0.1","5.7.0-0.2","5.7.0-0.3","5.7.2-0.1","5.7.2-0.2","5.7.2-0.3","5.7.2-0.4","5.8.2-1","5.8.2-1.1","5.8.2-1.2","5.8.4-1","5.9.0-0.1","5.9.0-0.2","5.9.1-0.1","5.9.2-1"]},{"source":"osv","ecosystem":"Debian:13","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.7.2-0.1","5.7.2-0.1+deb13u1","5.7.2-0.1+deb13u2","5.7.2-0.2","5.7.2-0.3","5.7.2-0.4","5.8.2-1","5.8.2-1.1","5.8.2-1.2","5.8.4-1","5.9.0-0.1","5.9.0-0.2","5.9.1-0.1","5.9.2-1"]},{"source":"osv","ecosystem":"Julia","package":"wolfSSL_jll","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.9.2+0"}]}]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.8+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.10.2+dfsg-2","3.12.0+dfsg-1","3.12.2+dfsg-1","3.13.0+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.1.0+dfsg-2","4.2.0+dfsg-1","4.2.0+dfsg-2","4.2.0+dfsg-3","4.3.0+dfsg-2"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.6.0-3","5.0.0-1","5.1.1-1","5.2.0-1","5.2.0-2"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.5.4-2","5.5.4-2.1","5.6.4-2","5.6.6-1.2","5.6.6-1.3","5.6.6-1.3build1"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.7.2-0.1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.9.1-0.1","5.9.2-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.7.2-0.1","5.8.2-1.2","5.8.4-1","5.9.1-0.1"]}],"products":[{"vendor":"wolfssl","product":"wolfssl"}],"references":[{"url":"https://github.com/wolfSSL/wolfssl/pull/10102","tags":["Issue Tracking","fix","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5503","tags":["advisory","web"]},{"url":"https://github.com/advisories/GHSA-65xm-pfx9-g5p3","tags":["web"]},{"url":"https://security.alpinelinux.org/vuln/CVE-2026-5503","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5503.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-5503","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-5503","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-5503","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-5503","title":"out-of-bounds write in TLSX_EchChangeSNI via attacker-controlled publicName","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-09T22:35:39.437Z","modified":"2026-04-10T17:58:51.312Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T13:39:27.849196Z"}],"euvd":[{"id":"EUVD-2026-21234","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-09T22:35:39Z","modified":"2026-04-10T17:58:51Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T19:24:29.850635Z"}],"ghsa":[{"id":"GHSA-65xm-pfx9-g5p3","title":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when...","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-10T00:30:31Z","modified":"2026-04-27T18:32:02Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/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":"medium"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","level":"critical"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T15:07:39.383876Z"}],"nvd":[{"id":"CVE-2026-5503","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-09T23:17:01.257Z","modified":"2026-06-17T10:59:08.027Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/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":"medium","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","level":"critical","assessor":"primary"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:12:13.902911Z"}],"osv":[{"id":"ALPINE-CVE-2026-5503","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-09T23:17:01.257Z","modified":"2026-11-03T06:33:06.247148362Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","level":"critical"}],"updated_at":"2026-11-03T07:15:37.282377Z"},{"id":"CVE-2026-5503","title":"out-of-bounds write in TLSX_EchChangeSNI via attacker-controlled publicName","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-09T22:35:39.437Z","modified":"2026-10-28T02:30:33.423794592Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T15:45:11.22012Z"},{"id":"DEBIAN-CVE-2026-5503","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-09T23:17:01.257Z","modified":"2026-10-01T03:03:26.54094463Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:45:57.236551Z"},{"id":"JLSEC-2026-731","title":"In `TLSX_EchChangeSNI`, the ctx-\u003eextensions branch set extensions unconditionally even when...","description":"In `TLSX_EchChangeSNI`, the ctx-\u003eextensions branch set extensions unconditionally even when `TLSX_Find` returned NULL. This caused `TLSX_UseSNI` to attach the attacker-controlled publicName to the shared `WOLFSSL_CTX` when no inner SNI was configured. `TLSX_EchRestoreSNI` then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing `TLSX_SNI_Write` to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-07-14T21:41:35.775Z","modified":"2026-07-25T18:24:50.577707058Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","level":"critical"},{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/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":"medium"}],"updated_at":"2026-11-02T15:47:19.003546Z"},{"id":"UBUNTU-CVE-2026-5503","description":"In TLSX_EchChangeSNI, the ctx-\u003eextensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.","status":"published","published":"2026-04-09T23:17:00Z","modified":"2026-10-17T13:00:27.307223148Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","level":"medium"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T16:56:41.382716Z"}]}}