Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expression dynamically using unescaped user input (the username parameter). An attacker can exploit this by sending a specially crafted username containing regex meta-characters (e.g., deeply nested groups or quantifiers), causing the MongoDB regex engine to consume excessive CPU resources. This can lead to Denial of Service for other users. The issue is fixed in version 2.3.3. To workaround this issue, implement a Web Application Firewall (WAF) rule to block requests containing regex meta-characters in the URL path.
History

Thu, 08 Jan 2026 19:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 08 Jan 2026 10:00:00 +0000

Type Values Removed Values Added
First Time appeared Flagforgectf
Flagforgectf flagforge
Vendors & Products Flagforgectf
Flagforgectf flagforge

Thu, 08 Jan 2026 00:30:00 +0000

Type Values Removed Values Added
Description Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expression dynamically using unescaped user input (the username parameter). An attacker can exploit this by sending a specially crafted username containing regex meta-characters (e.g., deeply nested groups or quantifiers), causing the MongoDB regex engine to consume excessive CPU resources. This can lead to Denial of Service for other users. The issue is fixed in version 2.3.3. To workaround this issue, implement a Web Application Firewall (WAF) rule to block requests containing regex meta-characters in the URL path.
Title Flag Forge has ReDoS Vulnerability in User Profile Lookup API
Weaknesses CWE-1333
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-01-08T19:06:16.315Z

Reserved: 2026-01-05T16:44:16.368Z

Link: CVE-2026-21868

cve-icon Vulnrichment

Updated: 2026-01-08T19:06:12.384Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-01-08T01:15:55.483

Modified: 2026-01-08T18:08:18.457

Link: CVE-2026-21868

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-01-08T09:47:43Z