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CVE-2026-96770

CRITICALCVSS 9.3/10EPSS 0.25%

Last modified

CVE-2026-96770 is a critical-severity vulnerability rated 9.3/10 on the CVSS scale. 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. EPSS estimates a 0.25% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 4.0
9.3/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.25%

15.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
Temporal Technologies, Inc.s2s-proxy>= 0.0.1-alpha, <= 0.2.2

References

Timeline

Published
Last Modified
Status
Deferred

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 severe is CVE-2026-96770?
CVE-2026-96770 has a CVSS score of 9.3/10 (CRITICAL severity). The EPSS model estimates a 0.25% probability of exploitation in the next 30 days.
How do I fix CVE-2026-96770?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST