s2s-proxy accepts untrusted client certificates
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · None
- Fix status
- No fix listed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
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 |
|---|---|---|---|---|---|
| Temporal Technologies, Inc. | s2s-proxy | 0.0.1-alpha – 0.2.2 | — | No fix listed | CNA |
- s2s-proxy VendorTemporal Technologies, Inc. Affected 0.0.1-alpha – 0.2.2 Fixed in — No fix listed CNA
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2026-96770
- 2026-10-03 Alias added: GHSA-fhc4-rg5x-86fx
References
More Temporal Technologies, Inc. vulnerabilities
- TI-2026-46800 temporalio/tchannel-go zero-chunk call fragment causes process termination CVSS 4.0HIGH 8.7
- TI-2026-46799 temporalio/tchannel-go malformed checksum type causes process termination CVSS 4.0HIGH 8.7
- TI-2026-46801 temporalio/ringpop-go fails to enforce configured label limits on inbound membership gossip CVSS 4.0HIGH 8.7
- TI-2026-13897 temporalio/sqlparser malformed MySQL version comments can cause a panic CVSS 4.0HIGH 8.7
- TI-2026-84119 Temporal Server k8s compute provider lets callers run host commands CVSS 4.0HIGH 8.7
- TI-2026-60383 Temporal Server worker deployment compute provider executes a caller-supplied command on the Worker Service host CVSS 4.0HIGH 8.7
Sources
- CVE-2026-96770 · CVE Program
- CVE-2026-96770 · NVD
- FIRST EPSS
- GHSA-fhc4-rg5x-86fx · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences