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Fencer Intel
critical 9.3

CVE-2026-89422 json

TLS 1.3 client skips server authentication when ServerHello carries an unsolicited pre_shared_key extension

published last mo. modified last mo. also EUVD-2026-84338 , GHSA-rgxr-4g4w-j875

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository erlang/otp. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
9.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

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.

Patch / fix

  • Erlang OTP 11.2.12.13, 11.6.0.6, 11.7.7, 27.3.4.18, 28.5.0.7, 29.1.1
  • erlang Debian 13 1:27.3.4.1+dfsg-1+deb13u4
  • erlang Debian 14 1:29.1.1+dfsg-1

debian advisories DEBIAN-CVE-2026-89422

  • erlang Ubuntu 22.04 LTS 1:24.2.1+dfsg-1ubuntu0.8
  • erlang Ubuntu 24.04 LTS 1:25.3.2.8+dfsg-1ubuntu4.8
  • erlang Ubuntu 26.04 LTS 1:27.3.4.6+dfsg-1ubuntu0.2
  • erlang Ubuntu Pro 20.04 LTS 1:22.2.7+dfsg-1ubuntu0.5+esm3

ubuntu advisories UBUNTU-CVE-2026-89422

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • erlang Azure Linux 3.0 26.2.5.21-8

azure linux advisories AZL-103428

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
last mo.

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/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

Affected products

  • Erlang OTP

Classification

Weakness
  • CWE-322 Key Exchange without Entity Authentication

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of erlang/otp published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.