{"id":"CVE-2019-12831","url":"https://www.cyber-defence.io/tools/cve/CVE-2019-12831","generatedAt":"2026-10-29T00:42:24.721Z","title":"In MyBB before 1.8.21, an attacker can abuse a default behavior of MySQL on many systems (that leads to truncation of strings that are too long for a database column) to create a PHP shell in the cache directory of a targeted forum via a crafted XML…","description":"In MyBB before 1.8.21, an attacker can abuse a default behavior of MySQL on many systems (that leads to truncation of strings that are too long for a database column) to create a PHP shell in the cache directory of a targeted forum via a crafted XML import, as demonstrated by truncation of aaaaaaaaaaaaaaaaaaaaaaaaaa.php.css to aaaaaaaaaaaaaaaaaaaaaaaaaa.php with a 30-character limit, aka theme import stylesheet name RCE.","published":"2019-06-15T18:29:00.000Z","lastModified":"2026-06-17T02:15:35.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.0","score":7.2,"severity":"HIGH","vector":"CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-20"],"affected":["mybb/mybb"],"epss":{"score":0.01467,"percentile":0.73567,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (1.47%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://blog.mybb.com/2019/06/10/mybb-1-8-21-released-security-maintenance-release/","tags":["Release Notes","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://blog.ripstech.com/2019/mybb-stored-xss-to-rce/","tags":["Exploit","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://blog.mybb.com/2019/06/10/mybb-1-8-21-released-security-maintenance-release/","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://blog.ripstech.com/2019/mybb-stored-xss-to-rce/","tags":["Exploit","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2019-12831","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}