TLS Configuration Flaw in s2s-proxy by Temporal
CVE-2026-96770

9.3CRITICAL

Key Information:

Vendor

Temporal Technologies, Inc.

Status
S2s-proxy
Vendor
CVE Published:
23 September 2026

What is CVE-2026-96770?

The s2s-proxy product has a significant TLS configuration issue where versions 0.1.16 through 0.2.2 utilize Go's RequireAnyClientCert mode incorrectly when skipCAVerification is set to false. This setup allows attackers to exploit the vulnerability by utilizing a self-signed certificate and private key to establish a TLS connection. Consequently, they can invoke remote procedure calls (RPCs) through the proxy without any validation of the certificate against the trusted Certificate Authority (CA). This presents a serious risk as deployment configurations may lack trusted certificates or required credentials.

Affected Version(s)

s2s-proxy 0.0.1-alpha <= 0.2.2

References

https://github.com/temporalio/s2s-proxy/blob/v0.2.2/encry...
product
https://github.com/temporalio/s2s-proxy/commit/d100c2258d...
product
https://github.com/temporalio/s2s-proxy/pull/296
patch

CVSS V4

Score:
9.3
Severity:
CRITICAL
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Praetorian, who reported this issue responsibly to Temporal Technologies
.