CVE-2026-96770 Details
Description
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.
A vulnerability exists in all published s2s-proxy versions through 0.2.2, where the TLS server listeners improperly verify client certificates. In versions 0.1.16 through 0.2.2, when 'skipCAVerification' is false, the server uses Go's 'RequireAnyClientCert' mode, which checks if the client possesses the certificate's private key but fails to validate the certificate against the configured Certificate Authority (CA). This allows an attacker to use a self-signed certificate to establish a TLS connection and invoke remote procedure calls (RPCs) using the proxy's configuration and Temporal credentials, without needing a certificate or key trusted by the deployment or any Temporal credential.
Users can upgrade to s2s-proxy version 0.2.3, where this vulnerability has been addressed by changing the TLS configuration to 'RequireAndVerifyClientCert', ensuring that client certificates are properly verified against the configured CA.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 23, 2026CISA-ADP
Assessed Sep 23, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-296 | Improper Following of a Certificate's Chain of Trust | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Temporal s2s-proxy | <= 0.2.2 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 23, 2026 | CVE Modified | CISA-ADP |
| Sep 23, 2026 | New CVE Received | [email protected] |