CVE-2025-13927
📋 TL;DR
This vulnerability in GitLab allows unauthenticated attackers to cause denial of service by sending specially crafted requests with malformed authentication data. It affects all GitLab Community Edition and Enterprise Edition installations running vulnerable versions. The attack requires no authentication and can disrupt service availability.
💻 Affected Systems
- GitLab Community Edition
- GitLab Enterprise Edition
📦 What is this software?
Gitlab by Gitlab
GitLab is a complete DevOps platform providing source code management, CI/CD pipelines, security scanning, container registry, and collaboration tools used by millions of developers and thousands of enterprises worldwide. As both a cloud-hosted SaaS offering (GitLab.com) and self-managed software, G...
Learn more about Gitlab →Gitlab by Gitlab
GitLab is a complete DevOps platform providing source code management, CI/CD pipelines, security scanning, container registry, and collaboration tools used by millions of developers and thousands of enterprises worldwide. As both a cloud-hosted SaaS offering (GitLab.com) and self-managed software, G...
Learn more about Gitlab →Gitlab by Gitlab
GitLab is a complete DevOps platform providing source code management, CI/CD pipelines, security scanning, container registry, and collaboration tools used by millions of developers and thousands of enterprises worldwide. As both a cloud-hosted SaaS offering (GitLab.com) and self-managed software, G...
Learn more about Gitlab →Gitlab by Gitlab
GitLab is a complete DevOps platform providing source code management, CI/CD pipelines, security scanning, container registry, and collaboration tools used by millions of developers and thousands of enterprises worldwide. As both a cloud-hosted SaaS offering (GitLab.com) and self-managed software, G...
Learn more about Gitlab →Gitlab by Gitlab
GitLab is a complete DevOps platform providing source code management, CI/CD pipelines, security scanning, container registry, and collaboration tools used by millions of developers and thousands of enterprises worldwide. As both a cloud-hosted SaaS offering (GitLab.com) and self-managed software, G...
Learn more about Gitlab →Gitlab by Gitlab
GitLab is a complete DevOps platform providing source code management, CI/CD pipelines, security scanning, container registry, and collaboration tools used by millions of developers and thousands of enterprises worldwide. As both a cloud-hosted SaaS offering (GitLab.com) and self-managed software, G...
Learn more about Gitlab →⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability for all GitLab users, disrupting development workflows, CI/CD pipelines, and code repository access.
Likely Case
Service degradation or temporary unavailability requiring administrator intervention to restore normal operations.
If Mitigated
Minimal impact with proper rate limiting, WAF rules, and network segmentation in place.
🎯 Exploit Status
Attack requires sending crafted HTTP requests with malformed authentication headers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 18.6.4, 18.7.2, or 18.8.2
Vendor Advisory: https://about.gitlab.com/releases/2026/01/21/patch-release-gitlab-18-8-2-released/
Restart Required: Yes
Instructions:
1. Backup your GitLab instance. 2. Update to patched version using your package manager. 3. Restart GitLab services. 4. Verify the update was successful.
🔧 Temporary Workarounds
Rate Limiting
allImplement rate limiting on authentication endpoints to reduce DoS impact
# Configure in GitLab nginx config or use external WAF
Network Segmentation
allRestrict access to GitLab instance to trusted networks only
# Use firewall rules to limit source IPs
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to block malformed authentication requests
- Deploy GitLab behind reverse proxy with request validation and rate limiting
🔍 How to Verify
Check if Vulnerable:
Check GitLab version against affected ranges: 11.9-18.6.3, 18.7.0-18.7.1, 18.8.0-18.8.1Check Version:
sudo gitlab-rake gitlab:env:info | grep 'Version:'Verify Fix Applied:
Confirm GitLab version is 18.6.4, 18.7.2, 18.8.2 or higher📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts from single IP
- Unusual malformed authentication headers in logs
- Increased error rates on authentication endpoints
Network Indicators:
- Spike in HTTP requests to authentication endpoints
- Requests with malformed Authorization headers
SIEM Query:
source="gitlab" AND ("malformed" OR "invalid" OR "bad request") AND auth*