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.
Metrics
Affected Vendors & Products
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History
Thu, 08 Jan 2026 19:15:00 +0000
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Thu, 08 Jan 2026 10:00:00 +0000
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| 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 |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-01-08T19:06:16.315Z
Reserved: 2026-01-05T16:44:16.368Z
Link: CVE-2026-21868
Updated: 2026-01-08T19:06:12.384Z
Status : Awaiting Analysis
Published: 2026-01-08T01:15:55.483
Modified: 2026-01-08T18:08:18.457
Link: CVE-2026-21868
No data.
OpenCVE Enrichment
Updated: 2026-01-08T09:47:43Z