CVE-2026-55952: TLS 1.3 server denial of service via malformed ClientHello pre-shared key extension

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-02 · updated 2026-10-25
Weakness: CWE-1284

Description

The Erlang/OTP ssl application does not validate that the PSK identity list and binder list carried in a TLS 1.3 ClientHello pre-shared key extension have equal length before passing them to the session ticket handler. In tls_handshake_1_3:handle_pre_shared_key/3, an OfferedPreSharedKeys record with a mismatched number of identities and binders is forwarded directly to tls_server_session_ticket:use/4, which crashes the session ticket handler process. An unauthenticated remote attacker can send a single crafted ClientHello to a TLS 1.3 server with session tickets enabled (stateful or stateless mode) and permanently disrupt session ticket handling on that listener. New TLS 1.3 handshakes complete but subsequently crash when the server attempts to issue a session ticket, effectively making TLS 1.3 unusable on the affected listener until the ssl application is restarted. TLS 1.2 connections are not affected. This issue affects OTP from OTP 22.2 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 9.5 before 11.7.3, 11.6.0.3 and 11.2.12.10.

Affected products

Erlang OTP: from 22.2 before 27.3.4.14; from 28.0 before 28.5.0.3; from 29.0 before 29.0.3 — fixed in 27.3.4.14, 28.5.0.3, 29.0.3
Erlang/Ssl: from 9.5 before 11.2.12.10; from 11.3 before 11.6.0.3; from 11.7 before 11.7.3 — fixed in 11.2.12.10, 11.6.0.3, 11.7.3

How to fix

Upgrade to a fixed version: Erlang OTP 27.3.4.14, 28.5.0.3, 29.0.3; Erlang/Ssl 11.2.12.10, 11.6.0.3, 11.7.3. Check the vendor advisory for mitigations.

References

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