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This vulnerability allows an authenticated user with specific project permissions to cause a severe denial of service (DoS) condition on the GitLab instance. The issue resides in the HTTP response processing mechanism. An attacker can construct and submit a malicious request that triggers the GitLab application to generate an HTTP response with a crafted “Location” header for a redirect. By exploiting logic flaws in how nested or recursive redirects are handled, the attacker can cause the server to enter an infinite processing loop or consume excessive resources (CPU/memory) while attempting to resolve the redirect chain. This exhausts available worker processes (e.g., Puma threads), making the GitLab web interface and API unresponsive to all other users. The attack requires a valid user account but not administrative privileges, significantly lowering the barrier for exploitation and enabling a single user to disrupt service for an entire organization.
Platform: GitLab CE/EE
Version: 8.3 to 18.4.4
Vulnerability: HTTP Redirect DoS
Severity: Critical
Date: 2025-11-26
Prediction: Patch 2025-12-10
What Undercode Say:
Analytics:
git clone https://gitlab.com/gitlab-org/gitlab.git cd gitlab git tag --contains $(git rev-parse fix_commit_hash) grep -r "Location:" app/controllers/ netstat -tulpn | grep :80
Example check for redirect logic before_action :validate_redirect_target def validate_redirect_target redirect_to params[:url] if unsafe_redirect?(params[:url]) end
How Exploit:
1. Attacker authenticates to GitLab.
2. Accesses feature with redirect parameter.
3. Crafts malicious URL causing recursive redirect.
4. Sends repeated requests to exhaust server threads.
Protection from this CVE:
Immediate upgrade to patched versions (18.4.5, 18.5.3, 18.6.1). Implement rate limiting per user. Apply WAF rules blocking malformed Location headers. Restrict user permissions via Least Privilege.
Impact:
Complete service unavailability. Productivity disruption for development teams. Potential data loss for in-progress operations.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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