{"id":"CVE-2026-121553","title":"Cotonti through 1.0.0 Predictable Validation Tokens via md5(microtime())","summary":"Cotonti through 1.0.0 generates registration and email-change validation tokens with md5(microtime()), allowing attackers to bypass email-ownership verification by predicting tokens. Attackers can derive the generation time from the HTTP…","severity":"medium","cvss":4.8,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L","cvssSource":"cna","cwe":["CWE-338"],"vendor":"cotonti","product":"cotonti","affected":["cotonti <= 1.0.0"],"ssvc":{"exploitation":"poc","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-07T03:09:24.645106Z"},"exploitAvailable":true,"published":"2026-11-03","updated":"2026-11-07","sourceUpdated":"2026-11-07T03:09:49.080Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-121553","references":[{"url":"https://github.com/Cotonti/Cotonti/issues/1904","label":"GitHub Issue #1904"},{"url":"https://github.com/Cotonti/Cotonti"},{"url":"https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.functions.php#L97"},{"url":"https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.profile.php#L116"},{"url":"https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.register.php#L148"},{"url":"https://github.com/Cotonti/Cotonti/pull/1905"},{"url":"https://www.vulncheck.com/advisories/cotonti-through-1.0.0-predictable-validation-tokens-via-md5-microtime","label":"VulnCheck Advisory: Cotonti through 1.0.0 Predictable Validation Tokens via md5(microtime())"}],"tags":["cve.org","exploit-available"],"epss":0.00355,"epssPercentile":0.29414,"ingestedAt":"2026-11-05T19:30:42.977Z","slug":"CVE-2026-121553","body":"## Overview\n\nCotonti through 1.0.0 generates registration and email-change validation tokens with md5(microtime()), allowing attackers to bypass email-ownership verification by predicting tokens. Attackers can derive the generation time from the HTTP Date header and compute candidate tokens offline. They then submit these tokens to the users.register.php validate handler to activate accounts or confirm email addresses they do not control.\n\n## Affected\n\n- `cotonti <= 1.0.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":38,"depthScoreParts":{"impact":26.4,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[{"seq":235763,"id":"CVE-2026-121553","ts":1794024606771,"field":"exploit_available","old":"false","new":"true"}]}