CVE-2026-96770

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.

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Weakness Type (CWE)

CWE-296 CWE-296

References

Other References

https://docs.temporal.io/production-deployment/data-encryption#codec-server-setup https://github.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go#L47-L62 https://github.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3b https://github.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3c https://github.com/temporalio/s2s-proxy/pull/296

Frequently Asked Questions

What is CVE-2026-96770? +

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.

How do I check if I'm vulnerable to CVE-2026-96770? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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