{"id":"CVE-2026-49953","aliases":["EUVD-2026-36793","GHSA-p3qj-vw7q-v9pc"],"status":"published","title":"Discuz! X5.0 CAPTCHA Bypass via Predictable Character Set","description":"Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.","severity":{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00359,"percentile":0.29942,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-804"],"published":"2026-06-15T18:45:19Z","modified":"2026-10-25T23:10:00Z","products":[{"vendor":"discuz!","product":"discuz! x5.0"}],"references":[{"url":"https://karmainsecurity.com/KIS-2026-10","tags":["technical-description"]},{"url":"https://karmainsecurity.com/chaining-bugs-in-discuz-from-race-condition-to-rce","tags":["exploit"]},{"url":"https://www.vulncheck.com/advisories/discuz-x5-0-captcha-bypass-via-predictable-character-set","tags":["third-party-advisory"]},{"url":"http://seclists.org/fulldisclosure/2026/Jun/4"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49953"},{"url":"https://github.com/advisories/GHSA-p3qj-vw7q-v9pc"}],"sources":{"cve":[{"id":"CVE-2026-49953","title":"Discuz! X5.0 CAPTCHA Bypass via Predictable Character Set","description":"Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.","status":"published","published":"2026-06-15T18:45:19.051Z","modified":"2026-07-28T01:49:38.986Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-804"],"updated_at":"2026-11-02T13:34:59.78118Z"}],"euvd":[{"id":"EUVD-2026-36793","description":"Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.","status":"published","published":"2026-06-15T18:45:19Z","modified":"2026-07-28T01:49:38Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T18:02:32.258903Z"}],"ghsa":[{"id":"GHSA-p3qj-vw7q-v9pc","title":"Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that...","description":"Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.","status":"published","published":"2026-06-15T21:30:40Z","modified":"2026-06-16T12:32:01Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/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","level":"medium"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-804"],"updated_at":"2026-11-02T15:08:48.16867Z"}],"nvd":[{"id":"CVE-2026-49953","description":"Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.","status":"published","published":"2026-06-15T20:16:29.26Z","modified":"2026-10-25T23:10:00.167Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/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","level":"medium","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-804"],"updated_at":"2026-11-02T14:12:23.846948Z"}]}}