CVE-2026-55953
Erlang/OTP TLS 1.2 and DTLS clients accept an anonymous cipher suite they never offered
Technology
Erlang/OTP
CVSS Score
7.4 / 10.0
Affected Versions
OTP 17.0 and later, before 27.3.4.15, 28.5.0.4 and 29.0.4 (ssl)
Upstream Fix
OTP 27.3.4.15, 28.5.0.4, 29.0.4
Published
July 27, 2026
OSSeva Coverage
Fixed upstream
Description
The ssl client for TLS 1.2 and earlier, and for DTLS, does not check that the cipher suite in the ServerHello was one it offered. An on-path attacker can pick an anonymous key exchange suite, which needs no server certificate, and so bypass verify_peer and read or change all traffic. TLS 1.3 connections are not affected, and the advisory's workaround is to use TLS 1.3 only. NVD scores it 7.4; the EEF's CVSS 4.0 score is 9.1.
Is your Erlang/OTP deployment affected?
If you're running OTP 17.0 and later, before 27.3.4.15, 28.5.0.4 and 29.0.4 (ssl), you need this patch. Book a discovery call to get covered.
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Running Erlang/OTP OTP 17.0 and later, before 27.3.4.15, 28.5.0.4 and 29.0.4 (ssl)?
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