CVE-2025-0186: GitLab Denial of Service Vulnerability

CVE-2025-0186 Overview

CVE-2025-0186 is a Denial of Service vulnerability affecting GitLab Community Edition (CE) and Enterprise Edition (EE) that allows an authenticated user to exhaust server resources by making crafted requests to a discussions endpoint. This resource exhaustion vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) can render GitLab instances unavailable, impacting development workflows and CI/CD pipelines across organizations.

Critical Impact

Authenticated attackers can cause service disruption by exhausting server resources through malicious requests to the discussions API endpoint, potentially affecting all users of the GitLab instance.

Affected Products

• GitLab Community Edition (CE) versions 10.6 to 18.9.5
• GitLab Enterprise Edition (EE) versions 10.6 to 18.9.5
• GitLab CE/EE versions 18.10.0 to 18.10.3
• GitLab CE/EE version 18.11.0

Discovery Timeline

• 2026-04-22 - GitLab releases security patch in version 18.11.1
• 2026-04-22 - CVE-2025-0186 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-0186

Vulnerability Analysis

This vulnerability stems from improper resource allocation controls in GitLab's discussions endpoint. When an authenticated user sends specially crafted requests to this endpoint, the server fails to properly limit resource consumption, leading to potential exhaustion of server memory, CPU, or other critical resources. The attack requires network access and low privileges (authenticated user), but does not require user interaction and can result in high availability impact.

The vulnerability affects a long lineage of GitLab versions dating back to version 10.6, indicating that the flawed code has been present in the codebase for an extended period. Organizations running self-managed GitLab instances are particularly at risk as they bear full responsibility for applying patches.

Root Cause

The root cause is classified as CWE-770: Allocation of Resources Without Limits or Throttling. The discussions endpoint lacks adequate rate limiting or resource allocation boundaries, allowing authenticated users to consume excessive server resources through repeated or malformed API requests. This design flaw permits unbounded resource allocation when processing discussion-related operations.

Attack Vector

The attack vector is network-based and requires authentication. An attacker with valid GitLab credentials can exploit this vulnerability by:

1. Authenticating to a vulnerable GitLab instance
2. Sending specially crafted requests to the discussions endpoint
3. Causing the server to allocate excessive resources without proper limits
4. Repeating requests to amplify the resource exhaustion effect

The vulnerability does not require any user interaction and can be exploited remotely. While confidentiality and integrity are not impacted, the availability impact is high, potentially causing complete service disruption.

The technical details of the crafted requests are documented in the HackerOne Report #2915694 and GitLab Work Item #511312.

Detection Methods for CVE-2025-0186

Indicators of Compromise

• Unusual spike in API requests to discussions-related endpoints
• Elevated server resource utilization (CPU, memory) without corresponding legitimate user activity
• Multiple rapid requests from authenticated accounts to discussion endpoints
• Server performance degradation or unresponsiveness during normal operating hours

Detection Strategies

• Monitor GitLab application logs for repeated requests to /api/v4/projects/:id/issues/:issue_iid/discussions and similar discussion endpoints
• Implement anomaly detection for API request patterns from individual authenticated users
• Track server resource metrics and alert on sudden spikes correlating with API activity
• Review authentication logs for accounts making unusually high volumes of discussion-related requests

Monitoring Recommendations

• Deploy application performance monitoring (APM) to track GitLab endpoint response times and resource consumption
• Configure alerts for memory and CPU utilization thresholds on GitLab servers
• Enable detailed API request logging with rate analysis capabilities
• Implement SentinelOne Singularity XDR to correlate network traffic patterns with system resource anomalies

How to Mitigate CVE-2025-0186

Immediate Actions Required

• Upgrade GitLab CE/EE to version 18.11.1, 18.10.4, or 18.9.6 immediately
• Review recent API access logs for suspicious discussion endpoint activity
• Implement rate limiting at the load balancer or reverse proxy level as an additional protection layer
• Monitor server resources closely until patches are applied

Patch Information

GitLab has released patched versions addressing this vulnerability:

• Version 18.11.1 - For installations running 18.11.x
• Version 18.10.4 - For installations running 18.10.x
• Version 18.9.6 - For installations running versions prior to 18.10

Patches are available through the official GitLab Patch Release 18.11.1. Organizations should follow their standard change management processes while prioritizing this update given the denial of service potential.

Workarounds

• Implement rate limiting on discussion-related API endpoints at the reverse proxy or load balancer level
• Configure web application firewall (WAF) rules to throttle requests to vulnerable endpoints
• Temporarily restrict API access for non-essential users until patches can be applied
• Monitor and temporarily disable accounts exhibiting suspicious API behavior

# Example NGINX rate limiting configuration for GitLab API
# Add to your NGINX configuration file

# Define rate limiting zone for API requests
limit_req_zone $binary_remote_addr zone=gitlab_api:10m rate=10r/s;

# Apply rate limiting to discussions endpoints
location ~ ^/api/v4/projects/.*/discussions {
    limit_req zone=gitlab_api burst=20 nodelay;
    proxy_pass http://gitlab-workhorse;
}