CVE-2025-14513: GitLab Protected Branches API DoS Vulnerability

CVE-2025-14513 Overview

CVE-2025-14513 is a denial of service vulnerability affecting GitLab CE/EE that allows unauthenticated attackers to disrupt service availability through improper input validation. The vulnerability exists in the protected branches API, where specially crafted JSON payloads can trigger a denial of service condition without requiring any authentication.

Critical Impact

Unauthenticated attackers can remotely cause denial of service to GitLab instances by sending malicious JSON payloads to the protected branches API, potentially disrupting development workflows and CI/CD pipelines for entire organizations.

Affected Products

• GitLab CE/EE versions 16.11 through 18.7.5
• GitLab CE/EE versions 18.8 through 18.8.5
• GitLab CE/EE versions 18.9 through 18.9.1

Discovery Timeline

• 2026-03-11 - CVE-2025-14513 published to NVD
• 2026-03-11 - GitLab releases security patch (versions 18.7.6, 18.8.6, and 18.9.2)
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2025-14513

Vulnerability Analysis

This vulnerability stems from improper input validation (CWE-1284) when the GitLab protected branches API processes incoming JSON payloads. The protected branches API endpoint is designed to manage branch protection rules, which control who can push to or merge into specific branches within a repository.

The flaw allows unauthenticated users to craft malicious JSON requests that exploit weaknesses in how the API validates and processes input data. When the API receives these specially crafted payloads, it fails to properly validate the input before processing, leading to resource exhaustion or application crashes that result in denial of service.

The network-accessible nature of this vulnerability, combined with no authentication requirement and no user interaction needed, makes it particularly dangerous for internet-facing GitLab instances. Organizations relying on GitLab for their software development lifecycle could experience significant disruption to their development workflows, code reviews, and CI/CD pipelines.

Root Cause

The root cause is CWE-1284 (Improper Validation of Specified Quantity in Input), where the protected branches API fails to adequately validate the structure, size, or content of JSON payloads before attempting to process them. This allows attackers to submit payloads that consume excessive resources or trigger unexpected behavior in the parsing logic.

Attack Vector

The attack is conducted remotely over the network by sending specially crafted HTTP requests containing malicious JSON payloads to the GitLab protected branches API endpoint. No authentication is required, meaning any network-accessible GitLab instance is potentially vulnerable. The attacker does not need any prior access to the GitLab instance, valid credentials, or user interaction to exploit this vulnerability.

The attack flow involves:

1. Identifying a vulnerable GitLab instance
2. Crafting a malicious JSON payload designed to exploit the input validation weakness
3. Sending the payload to the protected branches API endpoint
4. The vulnerable server processes the malicious input, leading to resource exhaustion or crash

Technical details regarding specific exploitation methods can be found in the HackerOne Report #3452477 and the GitLab Work Item.

Detection Methods for CVE-2025-14513

Indicators of Compromise

• Unusual volume of requests to protected branches API endpoints (/api/v4/projects/:id/protected_branches)
• Large or malformed JSON payloads in API request bodies
• Repeated 5xx server errors following API requests to protected branches endpoints
• Application crashes or service restarts correlated with API traffic patterns
• Memory or CPU spikes on GitLab application servers during API request processing

Detection Strategies

• Implement API request logging and monitor for abnormally sized JSON payloads targeting the protected branches API
• Configure web application firewall (WAF) rules to detect and block malformed JSON structures in API requests
• Monitor GitLab application logs for parsing errors or exceptions related to protected branches API processing
• Set up alerts for repeated unauthenticated API requests to sensitive endpoints from single IP addresses

Monitoring Recommendations

• Enable verbose logging for the GitLab API to capture detailed request information
• Monitor system resource utilization (CPU, memory) on GitLab application servers for anomalies
• Implement rate limiting on API endpoints, particularly for unauthenticated requests
• Use SentinelOne Singularity to monitor for process anomalies and resource exhaustion patterns on GitLab servers

How to Mitigate CVE-2025-14513

Immediate Actions Required

• Upgrade GitLab CE/EE to version 18.9.2, 18.8.6, or 18.7.6 depending on your current major version
• Implement rate limiting on the protected branches API endpoint to reduce exploitation impact
• Consider restricting API access to authenticated users only at the network or load balancer level
• Monitor GitLab instances for signs of exploitation attempts while planning the upgrade

Patch Information

GitLab has released patched versions that address this vulnerability:

• Version 18.9.2 - For installations on the 18.9.x branch
• Version 18.8.6 - For installations on the 18.8.x branch
• Version 18.7.6 - For installations on versions 16.11 through 18.7.x

Full patch details are available in the GitLab Patch Release Notice. Organizations should prioritize upgrading to the latest patched version for their deployment branch.

Workarounds

• Deploy a web application firewall (WAF) with rules to validate JSON payload sizes and structures for API requests
• Implement network-level access controls to restrict protected branches API access to trusted IP ranges
• Configure load balancers to rate limit requests to /api/v4/projects/*/protected_branches endpoints
• Consider temporarily disabling public API access if feasible until patches can be applied

# Example nginx rate limiting configuration for GitLab API
# Add to nginx configuration for GitLab
limit_req_zone $binary_remote_addr zone=protected_branches:10m rate=10r/s;

location ~ ^/api/v4/projects/.*/protected_branches {
    limit_req zone=protected_branches burst=20 nodelay;
    proxy_pass http://gitlab-workhorse;
}