CVE-2026-105236

Deferred Deferred - Pending Action

Improper Certificate Validation in Erlang/OTP SSL Application

Publication date: 2026-10-14

Last updated on: 2026-10-16

Assigner: EEF

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-14

Last Modified

2026-10-16

Generated

2026-10-19

AI Q&A

2026-10-15

EPSS Evaluated

2026-10-18

NVD

CVE-2026-105236

EUVD

EUVD-2026-101387

Affected Vendors & Products

Vendor	Product	Version / Range
Erlang	OTP	18.0
Erlang	OTP	7.0
Erlang	OTP	4fe38c4b8b2c8024afb60990e598ff823743fd54

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-295	The product does not validate, or incorrectly validates, a certificate.

Attack-Flow Graph

Executive Summary

This vulnerability in Erlang/OTP's SSL application allows a client with a certificate trusted by one SNI virtual host to authenticate to another SNI virtual host on the same listener by resuming a TLS 1.2 session. The session cache does not bind sessions to SNI names or client trust policies, and resumption does not revalidate the peer certificate against the CA for the requested name. TLS 1.3 is unaffected.

Detection Guidance

To detect this vulnerability, check if your Erlang/OTP SSL application is running versions affected by CVE-2026-105236. Use commands like 'erl -version' to verify the OTP version. Monitor TLS 1.2 session resumption logs for SNI mismatches between original and resumed sessions. Inspect network traffic for clients resuming sessions across different SNI hostnames sharing the same server certificate.

Impact Analysis

An attacker with a valid certificate for a lower-trust SNI name could resume a session at a higher-trust SNI name without proper validation, bypassing trust boundaries. This requires specific conditions: shared server certificate, TLS 1.2 enabled, default session reuse settings, and attacker possession of a legitimate certificate for the lower-trust SNI.

Compliance Impact

This vulnerability could impact compliance with GDPR and HIPAA by allowing unauthorized access to sensitive data. It enables a client with a lower-trust certificate to bypass trust boundaries and authenticate to a higher-trust SNI host, potentially violating data protection requirements that mandate strict access controls and trust validation.

Mitigation Strategies

Upgrade Erlang/OTP to patched versions (27.3.4.19, 28.5.0.8, or 29.1.2) to address the SNI session resumption issue.
Disable TLS 1.2 session reuse by setting 'reuse_sessions' to false in SSL configuration if upgrading is not immediately possible.
Separate SNI trust domains onto different listeners to prevent cross-SNI session resumption.
Restrict listeners to TLS 1.3 only, as it is unaffected by this vulnerability.

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