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CVE-2019-12831

N/A
Published: June 15, 2019 at 05:05 PM UTC
Updated: June 17, 2026 at 02:15 AM UTC
1 product affected across 1 vendorMybb

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Severity
N/A
Exploit prediction
EPSS 1%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mybb· Mybb
95%
v < 1.8.21
Affected range stops below 1.8.21, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

x_refsource_MISCRelease NotesVendor Advisory
Source: [email protected]
https://blog.mybb.com/2019/06/10/mybb-1-8-21-released-security-maintenance-release/
x_refsource_MISCExploitVendor Advisory
Source: [email protected]
https://blog.ripstech.com/2019/mybb-stored-xss-to-rce/

CVSS

6.5MEDIUM[email protected]
Confidentiality
PARTIAL
Integrity
PARTIAL
Availability
PARTIAL
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20

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