{"id":"CVE-2026-52767","state":"PUBLISHED","title":"YesWiki: Unauthenticated ActivityPub Signature-Verification Bypass via `!openssl_verify(...)` accepting `int(-1)`","description":"YesWiki is a wiki system written in PHP. From version 4.6.2 to before version 4.6.6, HttpSignatureService::verifySignature() checks the result of PHP's openssl_verify() with a loose boolean negation - if (!openssl_verify(...)) { throw ... }. PHP's openssl_verify has four possible return values: 1, 0, -1, and \"false\". The -1 row is the bypass: PHP's truthiness rules make -1 a truthy value, so !(-1) === false, the throw is skipped, and the controller proceeds to processActivity(). Any condition that makes OpenSSL's EVP_VerifyFinal() return -1 triggers the bypass. The reachable consequence is the controller silently treats a failed verification as success and processes the attacker's payload. This issue has been patched in version 4.6.6.","publishedAt":"2026-09-04T23:40:39.725Z","updatedAt":"2026-09-08T18:02:12.443Z","severity":{"score":8.2,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["YesWiki yeswiki"],"affected":[{"vendor":"YesWiki","product":"yeswiki","versions":[{"version":">= 4.6.2, < 4.6.6","status":"affected"}]}],"references":["https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g","https://github.com/YesWiki/yeswiki/commit/d1795e0301e1a1078f17b4b98f56fff70de2029e","https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6"],"weaknesses":["CWE-347"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/52xxx/CVE-2026-52767.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-52767","state":"PUBLISHED","datePublished":"2026-09-04T23:40:39.725Z","dateUpdated":"2026-09-08T18:02:12.443Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-08T17:13:43.064Z"},"containers":{"cna":{"title":"YesWiki: Unauthenticated ActivityPub Signature-Verification Bypass via `!openssl_verify(...)` accepting `int(-1)`","descriptions":[{"lang":"en","value":"YesWiki is a wiki system written in PHP. From version 4.6.2 to before version 4.6.6, HttpSignatureService::verifySignature() checks the result of PHP's openssl_verify() with a loose boolean negation - if (!openssl_verify(...)) { throw ... }. PHP's openssl_verify has four possible return values: 1, 0, -1, and \"false\". The -1 row is the bypass: PHP's truthiness rules make -1 a truthy value, so !(-1) === false, the throw is skipped, and the controller proceeds to processActivity(). Any condition that makes OpenSSL's EVP_VerifyFinal() return -1 triggers the bypass. The reachable consequence is the controller silently treats a failed verification as success and processes the attacker's payload. This issue has been patched in version 4.6.6."}],"affected":[{"vendor":"YesWiki","product":"yeswiki","versions":[{"version":">= 4.6.2, < 4.6.6","status":"affected"}]}],"references":[{"url":"https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g","name":"https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/YesWiki/yeswiki/commit/d1795e0301e1a1078f17b4b98f56fff70de2029e","name":"https://github.com/YesWiki/yeswiki/commit/d1795e0301e1a1078f17b4b98f56fff70de2029e","tags":["x_refsource_MISC"]},{"url":"https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6","name":"https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":8.2,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-347","lang":"en","description":"CWE-347: Improper Verification of Cryptographic Signature","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-04T23:40:39.725Z"},"source":{"advisory":"GHSA-mv28-wj57-f57g","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-08T17:51:20.326023Z","id":"CVE-2026-52767","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-08T18:02:12.443Z"}}]}}}