Temporal s2s-proxy up to 0.2.2 TLS Server Listener encryption/tls.go certificate validation

Summaryinfo

A vulnerability was found in Temporal s2s-proxy up to 0.2.2. It has been classified as problematic. This issue affects some unknown processing of the file encryption/tls.go of the component TLS Server Listener. The manipulation leads to certificate validation. This vulnerability is uniquely identified as CVE-2026-96770. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in Temporal s2s-proxy up to 0.2.2 and classified as problematic. This issue affects an unknown code block of the file encryption/tls.go of the component TLS Server Listener. The manipulation with an unknown input leads to a certificate validation vulnerability. Using CWE to declare the problem leads to CWE-295. The product does not validate, or incorrectly validates, a certificate. Impacted is integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-96770 since 09/23/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/23/2026). The attack technique deployed by this issue is T1587.003 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Firewall Software

Vendor

• Temporal

Name

• s2s-proxy

Version

• 0.2.0
• 0.2.1
• 0.2.2

CPE 2.3info

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CPE 2.2info

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