CVE-2021-26642
CWE-434Published: January 20, 2023· Updated: Jun 17, 2026
Official Description
When uploading an image file to a bulletin board developed with XpressEngine, a vulnerability in which an arbitrary file can be uploaded due to insufficient verification of the file. A remote attacker can use this vulnerability to execute arbitrary code on the server where the bulletin board is running.
Risk Analysis
XpressEngine bulletin boards are vulnerable to arbitrary file uploads due to insufficient file verification. This allows remote attackers to execute arbitrary code on the server, resulting in a critical 9.8 CVSS score.
No public exploit is currently known, and it is not in the CISA KEV. The flaw is remotely exploitable with low attack complexity.
Ensure the XpressEngine installation is updated and implement strict file type validation on all upload forms.
Technical Analysis
CVE-2021-26642 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (2)
Quick Facts
Related CVEs (CWE-434)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-26642 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts