Paper/Archive/CVE-2026-96770

CVE-2026-96770

Temporal Technologies, Inc. s2s-proxy — s2s-proxy accepts untrusted client certificates

Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
s2s-proxy0.0.1-alpha – 0.2.2–CNA

Scores by source

Temporal (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:H
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgithub.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go#L47-L62refgithub.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3bpatchgithub.com/temporalio/s2s-proxy/pull/296patchgithub.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3crefdocs.temporal.io/production-deployment/data-encryption#codec-server-setup