{"schemaVersion":3,"id":"CVE-2026-96770","aliases":[],"status":"published","duplicateOf":null,"title":null,"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.","dates":{"published":"2026-09-23T18:58:46.233Z","modified":"2026-09-23T19:36:12.488Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":9.3,"severity":"critical","version":"4.0","versionLabel":"v4.0","source":"CVE.org","vector":"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","computed":false,"selection":"backend-summary"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"CVE.org","score":9.3,"severity":"critical","vector":"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","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"NVD","score":9.3,"severity":"critical","vector":"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","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00254,"percentile":0.15978,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-09-24T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00254,"percentile":0.15978}],"last30":[{"date":"2026-09-24T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00254,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00254,"percentile":0.15978}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-296","name":"Improper Following of a Certificate's Chain of Trust","description":"The product does not follow, or incorrectly follows, the chain of trust for a certificate back to a trusted root certificate.","type":"weakness","status":"Draft","abstraction":"Base","likelihoodOfExploit":"Low","url":"https://cwe.mitre.org/data/definitions/296.html"}],"affected":[{"vendor":"temporal technologies, inc.","product":"s2s-proxy","name":"s2s-proxy","label":"s2s-proxy","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 0.0.1-alpha, ≤ 0.2.2","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 0.0.1-alpha, ≤ 0.2.2","eol":null,"hubHref":"/vendor/temporal_technologies_inc/s2s-proxy"}],"affectedCount":1,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go#L47-L62","label":"github.com/temporalio/s2s-proxy/blob/v0.2.2/encryption/tls.go","hostname":"github.com","tags":["Product"]},{"url":"https://github.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3b","label":"github.com/temporalio/s2s-proxy/commit/d100c2258dbc37d7df51298ea045315f36c7eb3b","hostname":"github.com","tags":["Product"]},{"url":"https://github.com/temporalio/s2s-proxy/pull/296","label":"github.com/temporalio/s2s-proxy/pull/296","hostname":"github.com","tags":["Patch"]},{"url":"https://github.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3c","label":"github.com/temporalio/s2s-proxy/commit/f1dc6b9a3919d37e82545ab461cbe6bb62618d3c","hostname":"github.com","tags":["Patch"]},{"url":"https://docs.temporal.io/production-deployment/data-encryption#codec-server-setup","label":"docs.temporal.io/production-deployment/data-encryption","hostname":"docs.temporal.io","tags":["Product"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-09-23T18:58:46.233Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-09-23T19:36:12.488Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":70,"level":"high","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-20T17:25:38.997Z","stale":false,"partial":false}}