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NVD description
Key Exchange without Entity Authentication vulnerability in Erlang/OTP ssl allows a peer that answers a TLS 1.3 client connection to impersonate the intended server. A pre_shared_key extension in the ServerHello that the client never offered causes the client to complete the handshake without validating the server's certificate, so ssl:connect returns {ok, Socket} against a peer holding no certificate, no private key and no prior session. tls_client_connection_1_3:handle_server_hello/2 passes the received extension to tls_gen_connection_1_3:handle_resumption/2, which sets resumption = true on its mere presence without checking that the client offered a PSK. tls_handshake_1_3:get_pre_shared_key/4 meanwhile falls back to the all-zero "no PSK" value and keys the handshake with the ordinary non-PSK schedule, so the attacker's own ephemeral key suffices. The resumption flag then routes maybe_resumption/1 straight to wait_finished, skipping the certificate-handling states, so certificate path validation, verify_fun, hostname verification, partial_chain, CRL checking and OCSP stapling are all bypassed. The default client configuration is affected; clients restricted to TLS 1.2 are not. This issue affects OTP from OTP 22.2 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1, corresponding to ssl from 9.5 before 11.2.12.13, 11.6.0.6, and 11.7.7.
Priority
LOW
Exploitation
NONE
PoC
NONE
Patch
NONE
Momentum
STABLE
Anyone who answers your Erlang TLS 1.3 connect can finish the handshake without a certificate. Default ssl:connect trusts them. They get your tokens and forge responses. https://hol.org/blog/cve-2026-89422-erlang-otp-tls13-unsolicited-psk-auth-bypass https://t.co/ilhswaweN1
🚨 ERLANG/OTP CRITICAL — TLS 1.3 CLIENT SKIPS SERVER AUTHENTICATION ON UNSOLICITED PSK Erlang/OTP has published a critical security advisory for CVE-2026-89422: a TLS 1.3 client flaw where an unsolicited ServerHello pre_shared_key extension can make ssl:connect succeed without Certificate / CertificateVerify checks. • Severity: Critical — CVSS 9.3 (CVSS:4.0) • GHSA: GHSA-rgxr-4g4w-j875 • Affected: OTP >= 22.2 until patched (default TLS 1.3 clients with verify_peer) • Impact: full server impersonation / MITM — attacker can hold traffic keys • Patched: OTP 29.1.1, 28.5.0.7, 27.3.4.18 (ssl 11.7.7 / 11.6.0.6 / 11.2.12.13) • Workaround until patched: restrict clients to TLS 1.2 (no TLS 1.3-safe configuration) • Credits: Milad Nasr and Luna Tong (Anthropic) ⚠️ Analyst Note: This is an official Erlang/OTP GitHub Security Advisory published September 22, 2026. Any application or platform using Erlang/OTP’s ssl client for TLS 1.3 with default verify_peer behavior should treat patching as urgent. A same-day High companion advisory (GHSA-qhcm-px9c-rvfh) covers SSH session channel exhaustion DoS after authentication and ships on the same patch trains — footnote only; the lead is the TLS 1.3 client auth skip. Official advisory: https://github.com/erlang/otp/security/advisories/GHSA-rgxr-4g4w-j875 #DDW #DarkWeb #CyberSecurity #ThreatIntelligence #Erlang #OTP #TLS
Erlang/OTP TLS 1.3 client will skip server cert checks if the ServerHello offers a PSK you never asked for CVE-2026-89422 / GHSA-rgxr-4g4w-j875, published Sept 22. A pre_shared_key extension the client did not offer completes the handshake with no certificate validation. Any ssl:connect path that negotiates TLS 1.3 (default), including httpc over HTTPS, is in scope. On-path or malicious server = full impersonation. Fixed in OTP 29.1.1 / 28.5.0.7 / 27.3.4.18. https://github.com/erlang/otp/security/advisories/GHSA-rgxr-4g4w-j875 #Cybersecurity #AI #AISecurity #MCP #Claude #GPT #Infosec #Trending #TLS #SupplyChain #AppSec
If I ran RabbitMQ this morning I'd check OTP first. CVE-2026-89422: TLS 1.3 peers can send an unsolicited PSK and your client skips every cert check (CVSS 9.3). Patch 27.3.4.18 / 28.5.0.7 / 29.1.1. No TLS 1.3-preserving workaround. https://app.opencve.io/cve/CVE-2026-89422
ssl:connect said ok. The peer had no cert and no key. CVE-2026-89422 in Erlang/OTP TLS 1.3: an unsolicited pre_shared_key skips every certificate check. Patch to 27.3.4.18, 28.5.0.7, or 29.1.1. Or pin TLS 1.2 until then. https://cna.erlef.org/cves/CVE-2026-89422.html
Patched in OTP 29.1.1 / 28.5.0.7 / 27.3.4.18 (CVE-2026-89422). Same bump clears SSH + ASN.1 DoS siblings. No TLS 1.3-preserving workaround. Upgrade, or force TLS 1.2 until you can.
CVE-2026-89422 Key Exchange without Entity Authentication vulnerability in Erlang/OTP ssl allows a peer that answers a TLS 1.3 client connection to impersonate the intended server. … https://www.cve.org/CVERecord?id=CVE-2026-89422