TI-2019-09612 Aliases CVE-2019-12831 GHSA-76pq-5fjf-j6xg

In MyBB before 1.8.21, an attacker can abuse a default behavior of MySQL on many systems…

LOW 35CWE-20Published 2019-06-15 · Updated 2024-08-04

Key facts

Attack vector: Network
Privileges required: High
User interaction: None
Attack complexity: Low
Impact type: —
Confidentiality · integrity · availability: High · High · High
Fix status: No fix listed

Attack profile from CVSS 3.0 · NVD. Fix status from CNA.

Summary

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.

Why it matters now

EPSS 0.01467 73rd percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
—	—	all versions	—	No fix listed	CNA

— Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:mybb:mybb::::::::	before 1.8.21	Vulnerable	mybb

cpe:2.3:a:mybb:mybb:*:*:*:*:*:*:*:* Versions before 1.8.21 Vulnerable ·mybb

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2019-12831
2026-10-03 Alias added: GHSA-76pq-5fjf-j6xg

References

Exploit 1

https://blog.ripstech.com/2019/mybb-stored-xss-to-rce/

Advisory 1

https://blog.mybb.com/2019/06/10/mybb-1-8-21-released-security-maintenance-release/

TI-2011-04621 myBB 1.6.4 Backdoor Arbitrary Command Execution CVSS 4.0CRITICAL 10.0
TI-2022-08548 Remote code execution in mybb CVSS 3.1HIGH 7.2
TI-2023-21959 MyBB before 1.8.36 allows Code Injection by users with certain high privileges. CVSS 3.1HIGH 7.2
TI-2022-18641 Mail settings' command parameter injection in mybb CVSS 3.1HIGH 7.2
TI-2025-21092 An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the… CVSS 3.1HIGH 7.6
TI-2025-21091 An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the… CVSS 3.1HIGH 7.6

See all 139 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences