CVE-2026-55953

The Erlang/OTP ssl TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client in ClientHello. The client-side tls_handshake:hello/5 handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to ssl_handshake:handle_server_hello_extensions/9, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected. An on-path attacker between the client and the intended server can respond with a ServerHello selecting an anonymous key exchange suite such as TLS_DH_anon_* or TLS_ECDH_anon_* that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire verify_peer and cacerts configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, and ssl:connect returns {ok, Socket}. All subsequent application traffic is readable and modifiable by the attacker. This issue affects OTP from OTP R13B03 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to ssl from 3.10.7 before 11.2.12.11, from 11.3 before 11.6.0.4, and from 11.7 before 11.7.4. Whether OTP before OTP R13B03, corresponding to ssl before 3.10.7, is affected is unknown.

• CWE-757

• https://cna.erlef.org/cves/CVE-2026-55953.htmlPatch, Third Party Advisory
• https://github.com/erlang/otp/commit/064e236414614f9085cbbbd6eacf0e43c02d1b4bPatch
• https://github.com/erlang/otp/commit/0a82596d425abe43dc2e0b3d74aa1557ef74051cPatch
• https://github.com/erlang/otp/commit/e6ff938116b2872bccc478af7fefb56627285b77Patch
• https://github.com/erlang/otp/security/advisories/GHSA-c6cw-pr89-w882Vendor Advisory
• https://osv.dev/vulnerability/EEF-CVE-2026-55953Patch, Third Party Advisory
• https://www.erlang.org/doc/system/versions.html#order-of-versionsRelease Notes

Published

Jul 27, 2026

Last Modified

Aug 10, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-55947Heap-based buffer overflow in Microsoft Office Excel allows …7.8
• CVE-2026-55948Use after free in Microsoft Office Excel allows an unauthori…7.8
• CVE-2026-55949Use of uninitialized resource in Microsoft Office Excel allo…7.8
• CVE-2026-5595A security vulnerability has been detected in griptape-ai gr…6.3
• CVE-2026-55950Time-of-check Time-of-use (TOCTOU) race condition vulnerabil…5.9
• CVE-2026-55952The Erlang/OTP ssl application does not validate that the PS…7.5
• CVE-2026-55954Authentication Bypass by Spoofing vulnerability in ueberauth…9.1
• CVE-2026-55955Improper Authentication vulnerability in Apache Tomcat allow…6.5
• CVE-2026-55956Improper Authorization vulnerability in Apache Tomcat leads …6.5
• CVE-2026-55957Missing Critical Step in Authentication vulnerability in Apa…7.3
• CVE-2026-55958Out-of-bounds write in the Renesas TSIP TLS 1.3 transcript b…7.5
• CVE-2026-5596A vulnerability was detected in griptape-ai griptape 0.19.4.…6.3