CVE-2026-96770s2s-proxy accepts untrusted client certificates
Updated under an hour ago ()
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It affects Temporal Technologies, Inc. s2s-proxy. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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All published s2s-proxy versions through 0.2.2 are affected. In versions 0.1.16 through 0.2.2, TLS server listeners use Go's RequireAnyClientCert mode when skipCAVerification is false. This mode checks that the client holds the certificate's private key but does not verify the certificate against the configured CA. An attacker can therefore use a self-signed certificate and key to establish a TLS and yamux connection, then invoke RPCs allowed by the proxy's configuration and Temporal credentials. No certificate or private key trusted by the deployment, and no Temporal credential, is required.
- CVSS
- 9.3 CRITICAL (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:H
- Weakness (CWE)
- CWE-296
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Temporal
- NVD analysis
- Deferred
- Record last updated
- Sep 23, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Temporal Technologies, Inc. s2s-proxy temporal_technologies:s2s_proxy (from the name) | from 0.0.1-alpha through 0.2.2 | CNA record |
References
- https://github.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go#L47-L62product
- https://github.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3bproduct
- https://github.com/temporalio/s2s-proxy/pull/296patch
- https://github.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3cpatch
- https://docs.temporal.io/production-deployment/data-encryption#codec-server-setupproduct
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.