CVE-2026-89422: TLS 1.3 client skips server authentication when ServerHello carries an unsolicited pre_shared_key extension
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.5%
EPSS score, percentile 39.8 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 9.3 Critical
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
- Which versions are affected?
Affected
- 22.2
- 9.5
Unaffected from 27.3.4.18; from 28.5.0.7; from 29.1.1; from 11.2.12.13; from 11.6.0.6; from 11.7.7
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Workaround (from the CVE record)
Restrict affected clients to TLS 1.2 by setting {versions, ['tlsv1.2']} in the client's ssl options. This avoids the vulnerable code path at the cost of losing TLS 1.3. No configuration both keeps TLS 1.3 and mitigates the issue.
Advisories and patches
- Fix commit afec515 in erlang/otp
- Fix commit 98c66c8 in erlang/otp
- Fix commit fd1d9d0 in erlang/otp
- GitHub Advisory
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 22.2 |
| Unaffected | from 27.3.4.18 |
| Unaffected | from 28.5.0.7 |
| Unaffected | from 29.1.1 |
Versions not listed are: unaffected.
| Status | Versions |
|---|---|
| Affected | 9.5 |
| Unaffected | from 11.2.12.13 |
| Unaffected | from 11.6.0.6 |
| Unaffected | from 11.7.7 |
Versions not listed are: unaffected.
| Status | Versions |
|---|---|
| Affected | 21b8a1b0ad0a |
| Unaffected | from afec5156361b |
| Unaffected | from 98c66c858113 |
| Unaffected | from fd1d9d07fc92 |
Versions not listed are: unaffected.
Versions the record lists as unaffected: 27.3.4.18, 28.5.0.7, 29.1.1, 11.2.12.13, 11.6.0.6, 11.7.7, afec5156361bb50d3607c7c1a453c19b9149b324, 98c66c858113949c4262d26cd7d426c4b09d2b35.
Source: CVE List, as of . About the data.
About this vulnerability
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 certif…
Summary: CVE record, as of .
- CISA has not added CVE-2026-89422 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 22 Sep 2026.
- The CVE record carries a CVSS v4.0 base score of 9.3 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.5% (percentile 39.8), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact total.
- The credits in the CVE record name Anthropic (Claude) as finder.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
TLS 1.3 client skips server authentication when ServerHello carries an unsolicited pre_shared_key extension
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.
Source: CVE List, as of . About the data.
Weakness
CWE-322, 1 CAPEC
- CWE-322: Key Exchange without Entity Authentication
Attack patterns (CAPEC)
- CAPEC-94: An attacker that answers a TLS 1.3 client connection, either as the host the client dials or as an on-path attacker, completes the handshake as the intended se…
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published |
References
4
Known exploited Erlang vulnerabilities
- CVE-2025-32433: Erlang Erlang/OTP SSH Server Missing Authentication for Critical Function Vulnerability