CVE-2026-96770: Temporal Technologies s2s-proxy · Improper Following of a Certificate's Chain of Trust
Affects Temporal Technologies s2s-proxySource CVE Database V5
Not known to be exploited · CVSS 9.3 Critical.
Data as of 7 Nov 2026, 23:24 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 25% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:HExploitation evidence
Disclosed: evidence found.
CVE published 23 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Temporal Technologies, Inc.s2s-proxy | Affected
| Fixed in– |
Gogithub.com/temporalio/s2s-proxypkg:golang/github.com/temporalio/s2s-proxyOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Until a fix is available, deployments should consider disabling or restricting the affected TLS server listener configurations or applying additional network-level controls to limit exposure.
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.
References
- github.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go (opens in a new tab)
- github.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3b (opens in a new tab)
- github.com/temporalio/s2s-proxy/pull/296 (opens in a new tab)
- github.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3c (opens in a new tab)
- docs.temporal.io/production-deployment/data-encryption (opens in a new tab)