TLS 1.3 server denial of service via malformed ClientHello pre-shared key extension
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 1 fixed, 3 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Erlang | OTP | 9.5 and later | — | No fix listed | CNA |
| Erlang | OTP | 22.2 and later | — | No fix listed | CNA |
- OTP VendorErlang Affected 9.5 and later Fixed in — No fix listed CNA
- OTP VendorErlang Affected 22.2 and later Fixed in — No fix listed CNA
CPE configurations NVD · 2
Remediation
Red Hat 1 advisory
- RHSA-2026:63160 Released 2026-09-03 · Red Hat rating ImportantRed Hat Hardened Images RPMs bug fix and enhancement update
- Red Hat Hardened Images erlang27-27.3.4.17-1.hum1@aarch64, erlang27-27.3.4.17-1.hum1@src, erlang27-27.3.4.17-1.hum1@x86_64 +47
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenStack Platform 16.2 | Affected | No fix yet |
| Red Hat OpenStack Platform 17.1 | Affected | No fix yet |
| Red Hat OpenStack Platform 18.0 | Affected | No fix yet |
| Red Hat Hardened Images | Fixed | RHSA-2026:63160 |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-55952
References
Patch 3
Advisory 3
More Erlang/otp vulnerabilities
- TI-2025-23504 Erlang/OTP SSH Vulnerable to Pre-Authentication RCE KEVCVSS 3.1CRITICAL 10.0
- TI-2023-26623 The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6… CVSS 3.1MEDIUM 5.9
- TI-2017-14604 The Erlang otp TLS server answers with different TLS alerts to different error types in… CVSS 3.0MEDIUM 5.9
- TI-2026-36669 Stack buffer overflow in SCTP error cause parsing in inet_drv allows remote VM crash CVSS 4.0HIGH 8.8
- TI-2022-17230 In Erlang/OTP before 23.3.4.15, 24.x before 24.3.4.2, and 25.x before 25.0.2, there is a… CVSS 3.1CRITICAL 9.8
- TI-2016-08327 An issue was discovered in Erlang/OTP 18.x. CVSS 3.0CRITICAL 9.8
Sources
- CVE-2026-55952 · CVE Program
- CVE-2026-55952 · NVD
- FIRST EPSS
- CVE-2026-55952 · Red Hat security data · CC BY 4.0
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