EUVD Vulnerability Catalog
EUVD-2026-85567
Severity: CRITICAL
Base Score: 9.3
CVSS Version: 4.0
Vulnerability 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.
CVSS Vector Analysis
Below is the complete, human-readable breakdown of the CVSS metric string: 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
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Attack Vector (AV): Network
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Attack Complexity (AC): Low
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Attack Requirements (AT): None
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Privileges Required (PR): None
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User Interaction (UI): None
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Vulnerability Confidentiality Impact (VC): None
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Vulnerability Integrity Impact (VI): High
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Vulnerability Availability Impact (VA): None
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Subsequent Confidentiality Impact (SC): High
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Subsequent Integrity Impact (SI): High
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Subsequent Availability Impact (SA): High
Affected Vendors & Systems
Vendor
Temporal Technologies, Inc.
References & Advisory Links
- https://github.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go#L47-L62
- https://github.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3b
- https://github.com/temporalio/s2s-proxy/pull/296
- https://github.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3c
- https://docs.temporal.io/production-deployment/data-encryption#codec-server-setup
Metadata Profile
Database Authority
European Union Agency for Cybersecurity (ENISA) EUVD
Assigner
Temporal
EPSS Probability
0
Known Aliases
CVE-2026-96770
Published On
2026-09-23
Last Updated
2026-09-23