CVE-2019-12831

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.

• CWE-20

• https://blog.mybb.com/2019/06/10/mybb-1-8-21-released-security-maintenance-release/Release Notes, Vendor Advisory
• https://blog.ripstech.com/2019/mybb-stored-xss-to-rce/Exploit, Vendor Advisory
• https://blog.mybb.com/2019/06/10/mybb-1-8-21-released-security-maintenance-release/Release Notes, Vendor Advisory
• https://blog.ripstech.com/2019/mybb-stored-xss-to-rce/Exploit, Vendor Advisory

Published

Jun 15, 2019

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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