{"id":"CVE-2026-52767","summary":"YesWiki: Unauthenticated ActivityPub Signature-Verification Bypass via `!openssl_verify(...)` accepting `int(-1)`","details":"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.","aliases":["GHSA-mv28-wj57-f57g"],"modified":"2026-09-06T03:46:13.606257554Z","published":"2026-09-04T23:40:39.725Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-347"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52767.json"},"references":[{"type":"WEB","url":"https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52767.json"},{"type":"ADVISORY","url":"https://github.com/YesWiki/yeswiki/security/advisories/GHSA-mv28-wj57-f57g"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52767"},{"type":"FIX","url":"https://github.com/YesWiki/yeswiki/commit/d1795e0301e1a1078f17b4b98f56fff70de2029e"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/yeswiki/yeswiki","events":[{"introduced":"396b5fb891fdeca1a010c97d3cfe4d7ff897110b"},{"fixed":"fa81922f4103630911cbea98ead3c4b7bc786e19"}],"database_specific":{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"4.6.2"},{"fixed":"4.6.6"}]}}],"versions":["v4.6.5","v4.6.4","v4.6.3","v4.6.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52767.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L"}]}