Vulnerability · Published Oct 14, 2026 · Assigned by EEF
CVE-2026-105236TLS 1.2 session resumption in ssl crosses SNI virtual-host client-certificate trust boundaries
Medium 6.3
In plain English
A medium-severity improper certificate validation in OTP from Erlang. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Improper Certificate Validation vulnerability in the ssl application in Erlang/OTP allows a client that holds a certificate trusted by one SNI virtual host to authenticate to a second SNI virtual host on the same listener by resuming its TLS 1.2 session there. A server that serves several SNI names from one listen socket through sni_fun or sni_hosts keeps one pre-TLS 1.3 session cache per listener and does not bind a cached session to the SNI name or client trust policy that established it. When an SNI option set switches to verify_peer without naming reuse_sessions, ssl_config:update_options/3 inherits the base listener's reuse_sessions value of true, so the default that disables reuse for client-authenticating servers does not apply. On an abbreviated handshake ssl_session:is_resumable/4 checks only that the cached session uses one of the current server certificates and carries some peer certificate, and never revalidates that certificate against the CA selected for the requested name. The names must share a server certificate, which is common with wildcard or multi-SAN certificates. TLS 1.3 does not use this cache and is not affected. This issue affects OTP from OTP 18.0 before OTP 27.3.4.19, OTP 28.5.0.8, and OTP 29.1.2, corresponding to ssl from 7.0 before 11.2.12.14, 11.6.0.7, and 11.7.8.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | erlang | no fix listed | DEBIAN-CVE-2026-105236 |
| Debian:13 | erlang | no fix listed | DEBIAN-CVE-2026-105236 |
| Debian:14 | erlang | 1:29.1.2+dfsg-1 | DEBIAN-CVE-2026-105236 |
| Ubuntu:22.04:LTS | erlang | no fix listed | UBUNTU-CVE-2026-105236 |
| Ubuntu:24.04:LTS | erlang | no fix listed | UBUNTU-CVE-2026-105236 |
| Ubuntu:26.04:LTS | erlang | no fix listed | UBUNTU-CVE-2026-105236 |
| Ubuntu:26.10 | erlang | no fix listed | UBUNTU-CVE-2026-105236 |
Affected products (as reported)
Weakness: CWE-295 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
References
- GitHub Advisory related, vendor-advisory
- EEF CNA record for CVE-2026-105236 related
- OSV record EEF-CVE-2026-105236 related
- Erlang/OTP version ordering x_version-scheme
- Introducing commit 4fe38c4 in erlang/otp related
- Fix commit 0c20f36 in erlang/otp patch
- Fix commit 4d76adb in erlang/otp patch
- Fix commit 10ee925 in erlang/otp patch