CVE-2026-21868
7.5 · HIGHOverview
CVE-2026-21868 is a high-severity vulnerability affecting flagforge flagforge. It was published on January 8, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from flagforge. Update flagforge to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| flagforge | flagforge | >= 2.0, < 2.3.3 | Affected |
Frequently Asked Questions
What is CVE-2026-21868?
CVE-2026-21868 is a high-severity vulnerability affecting flagforge flagforge. It was published on January 8, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).
How severe is CVE-2026-21868?
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-21868?
Check the references section for vendor advisories and patches from flagforge. Update flagforge to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-21868?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-21868 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
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