{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-45734","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-05-13T05:51:48.667Z","datePublished":"2026-08-18T15:51:07.257Z","dateUpdated":"2026-08-19T14:43:38.996Z"},"containers":{"cna":{"title":"MyBB: Default CAPTCHA missing invalidation","problemTypes":[{"descriptions":[{"cweId":"CWE-837","lang":"en","description":"CWE-837: Improper Enforcement of a Single, Unique Action","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","version":"3.1"}}],"references":[{"name":"https://github.com/mybb/mybb/security/advisories/GHSA-jrrr-f3jw-mjmc","tags":["x_refsource_CONFIRM"],"url":"https://github.com/mybb/mybb/security/advisories/GHSA-jrrr-f3jw-mjmc"},{"name":"https://github.com/mybb/mybb/commit/c2ed54f9259b9ce05728a9e657169033fe4adffc","tags":["x_refsource_MISC"],"url":"https://github.com/mybb/mybb/commit/c2ed54f9259b9ce05728a9e657169033fe4adffc"},{"name":"https://github.com/mybb/mybb/releases/tag/mybb_1840","tags":["x_refsource_MISC"],"url":"https://github.com/mybb/mybb/releases/tag/mybb_1840"},{"name":"https://mybb.com/versions/1.8.40","tags":["x_refsource_MISC"],"url":"https://mybb.com/versions/1.8.40"}],"affected":[{"vendor":"mybb","product":"mybb","versions":[{"version":"< 1.8.40","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-08-18T15:51:07.257Z"},"descriptions":[{"lang":"en","value":"MyBB is free and open source forum software. Prior to 1.8.40, the built-in CAPTCHA does not consistently enforce single-use semantics, allowing remote attackers to bypass CAPTCHA controls through challenge replay. The successful validation paths in contact.php, member.php?action=do_resendactivation, member.php?action=do_lostpw, member.php?action=do_emailuser, and sendthread.php?action=do_sendtofriend do not call captcha::invalidate_captcha() for the MyBB Default CAPTCHA selected by the captchaimage setting. A valid response can therefore be reused until a non-vulnerable endpoint invalidates it, an incorrect response is submitted, or the challenge expires. This issue is fixed in version 1.8.40."}],"source":{"advisory":"GHSA-jrrr-f3jw-mjmc","discovery":"UNKNOWN"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-19T14:43:20.441189Z","id":"CVE-2026-45734","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-08-19T14:43:38.996Z"}}]}}