---
id: CVE-2026-96770
title: All published s2s-proxy versions through 0.2.2 are affected
summary: >-
  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
  certifica…
severity: critical
cvss: 9.3
cvssVector: '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'
cwe:
  - CWE-296
vendor: 'Temporal Technologies, Inc.'
product: github.com/temporalio/s2s-proxy
affected:
  - github.com/temporalio/s2s-proxy >= 0.0.1-alpha <= 0.2.2
published: '2026-09-23'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T20:43:32.537'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-96770'
references:
  - url: >-
      https://docs.temporal.io/production-deployment/data-encryption#codec-server-setup
    label: security@temporal.io
  - url: >-
      https://github.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go#L47-L62
    label: security@temporal.io
  - url: >-
      https://github.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3b
    label: security@temporal.io
  - url: >-
      https://github.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3c
    label: security@temporal.io
  - url: 'https://github.com/temporalio/s2s-proxy/pull/296'
    label: security@temporal.io
tags:
  - nvd
  - cve.org
epss: 0.00254
epssPercentile: 0.15102
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-09-23T19:36:07.279659Z'
cvssSource: cna
ingestedAt: '2026-09-23T19:31:04.478Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.