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

Status: published. Published: 2026-07-02. Updated: 2026-11-11.

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 27.3.4.14, OTP 28.5.0.3, and OTP 29.0.3, corresponding to ssl from 9.5 before 11.2.12.10, 11.6.0.3, and 11.7.3.

## Remediation

- workaround: * Disable session tickets on TLS 1.3 servers by setting session_tickets to disabled in the server's ssl options.
* Restrict the server to TLS 1.2 by setting versions to ['tlsv1.2'] in the server's ssl options. (source: CNA: EEF)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/095f744713c325acdbd18c23e397f04593c06275
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/e77823e6d980b2ec0b4fe4ea3f2d098ca239e3ce
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/2c3e599797644310e5d4aa39c7193420e59dadff
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/erlang/otp/commit/9b5437c72fa3403a75c1aba28e5c532bc191c662

## Affected products and versions

- Erlang / OTP (otp): ≥ 22.2; < * (affected, otp); unaffected at 27.3.4.14; unaffected at 28.5.0.3; unaffected at 29.0.3. Source: CNA: EEF
- Erlang / OTP (ssl): ≥ 9.5; < * (affected, otp); unaffected at 11.2.12.10; unaffected at 11.6.0.3; unaffected at 11.7.3. Source: CNA: EEF
- Erlang / OTP (erlang/otp): ≥ 339a279f02ce38a7b23010e56000613e19abb21f; < * (affected, git); unaffected at 095f744713c325acdbd18c23e397f04593c06275; unaffected at e77823e6d980b2ec0b4fe4ea3f2d098ca239e3ce; unaffected at 2c3e599797644310e5d4aa39c7193420e59dadff; unaffected at 9b5437c72fa3403a75c1aba28e5c532bc191c662. Source: CNA: EEF

## Severity and prioritization

- CVSS 4.0: 8.2 (high); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: EEF

- CISA KEV: No listing in collected sources

- EPSS: 0.48% as of 2026-11-10; percentile 41.78%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-1284

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/erlang/otp/security/advisories/GHSA-8c57-44c9-pc59 (CNA: EEF; vendor-advisory, related)

- https://cna.erlef.org/cves/CVE-2026-55952.html (CNA: EEF; related)

- https://osv.dev/vulnerability/EEF-CVE-2026-55952 (CNA: EEF; related)

- https://www.erlang.org/doc/system/versions.html#order-of-versions (CNA: EEF; x_version-scheme)

- https://github.com/erlang/otp/commit/339a279f02ce38a7b23010e56000613e19abb21f (CNA: EEF; related)

- https://github.com/erlang/otp/commit/095f744713c325acdbd18c23e397f04593c06275 (CNA: EEF; patch)

- https://github.com/erlang/otp/commit/e77823e6d980b2ec0b4fe4ea3f2d098ca239e3ce (CNA: EEF; patch)

- https://github.com/erlang/otp/commit/2c3e599797644310e5d4aa39c7193420e59dadff (CNA: EEF; patch)

- https://github.com/erlang/otp/commit/9b5437c72fa3403a75c1aba28e5c532bc191c662 (CNA: EEF; patch)

## Provenance

- CNA: EEF: https://www.cve.org/CVERecord?id=CVE-2026-55952; retrieved 2026-11-11; source updated 2026-11-11

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-55952; retrieved 2026-11-11; source updated Not reported

Revision: e4897e945a6957ffe92b2d221484c442b9cb0d641cee309c50032e01cc55536e

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