Improper input validation in Mybb
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.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.2 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.015 (73.1th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 73rd percentile — 73.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.015 · newest: 0.015 · change: 0.000
Affected products
Weakness classification (CWE)
References
- blog.ripstech.com/2019/mybb-stored-xss-to-rce/ (Exploit, Vendor Advisory)
- blog.mybb.com/2019/06/10/mybb-1-8-21-released-security-maintenance-release/ (Release Notes, Vendor Advisory)
Frequently asked questions
- What is CVE-2019-12831?
- CVE-2019-12831 is a high-severity vulnerability in Mybb, classified under Improper Input Validation. CVSS score: 7.2/10. Published 2019-06-15.
- How severe is CVE-2019-12831?
- High severity. CVSS v3 base score is 7.2 out of 10.