CVE-2025-12576: GitLab CE/EE DoS Vulnerability

CVE-2025-12576 Overview

A denial of service vulnerability has been identified in GitLab CE/EE that allows an authenticated user to cause service disruption through improper handling of webhook response data. The vulnerability affects all GitLab versions from 9.3 and stems from inadequate resource management when processing webhook responses, enabling attackers with valid credentials to exhaust system resources.

Critical Impact

Authenticated users can leverage malicious webhook responses to trigger resource exhaustion, potentially causing denial of service conditions that impact GitLab availability for all users of the affected instance.

Affected Products

• GitLab CE/EE versions 9.3 through 18.7.5
• GitLab CE/EE versions 18.8.0 through 18.8.5
• GitLab CE/EE versions 18.9.0 through 18.9.1

Discovery Timeline

• 2026-03-11 - CVE CVE-2025-12576 published to NVD
• 2026-03-11 - GitLab releases security patch in version 18.9.2
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2025-12576

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The flaw exists in GitLab's webhook handling mechanism, which fails to properly validate and limit the resources consumed when processing webhook response data. Under certain conditions, an authenticated attacker can craft or manipulate webhook responses that cause the application to allocate excessive resources, leading to denial of service.

The attack is network-accessible and requires low privileges to execute. While the vulnerability does not impact data confidentiality or integrity, it poses a significant availability risk to GitLab instances. The attack complexity is low, meaning exploitation does not require specialized conditions or circumstances beyond having valid authentication credentials.

Root Cause

The root cause of this vulnerability lies in improper resource allocation controls within GitLab's webhook response processing logic. When webhook responses are received, the application fails to enforce appropriate limits on memory allocation or processing time. This lack of throttling allows maliciously crafted or abnormally large webhook responses to consume disproportionate system resources, ultimately degrading or denying service to legitimate users.

Attack Vector

The attack vector is network-based, requiring an authenticated user to trigger the vulnerability. An attacker with valid credentials to a GitLab instance can configure or interact with webhooks in a manner that produces responses the application cannot handle efficiently. The improper handling of these responses leads to resource exhaustion.

The vulnerability can be exploited through the following general approach:

1. An authenticated attacker identifies or creates a webhook configuration in GitLab
2. The attacker manipulates the webhook endpoint or response characteristics to generate problematic response data
3. When GitLab processes the webhook response, improper resource handling causes memory or CPU exhaustion
4. Continued exploitation can render the GitLab instance unresponsive to legitimate users

For technical implementation details, refer to the HackerOne Security Report #3395198 and the GitLab Work Item Documentation.

Detection Methods for CVE-2025-12576

Indicators of Compromise

• Unusual memory consumption spikes correlated with webhook processing activities
• Increased response times or timeouts on GitLab web interface during webhook executions
• Error logs showing resource allocation failures or memory warnings in webhook-related processes
• Abnormal patterns of webhook requests or responses from specific authenticated users

Detection Strategies

• Monitor GitLab application logs for webhook-related errors, timeouts, or resource exhaustion messages
• Implement alerting on abnormal memory and CPU utilization patterns in GitLab processes
• Review webhook configurations for suspicious endpoints or recently modified webhook settings
• Audit authenticated user activities related to webhook creation and modification

Monitoring Recommendations

• Configure resource monitoring dashboards to track GitLab process memory and CPU usage over time
• Set up automated alerts when webhook processing times exceed normal thresholds
• Enable detailed logging for webhook transactions to capture response sizes and processing durations
• Regularly review and audit webhook configurations across all projects and groups

How to Mitigate CVE-2025-12576

Immediate Actions Required

• Upgrade GitLab CE/EE to version 18.9.2, 18.8.6, or 18.7.6 depending on your current version branch
• Review and audit existing webhook configurations for suspicious or unnecessary entries
• Temporarily disable non-essential webhooks until the patch is applied
• Monitor system resources closely for signs of exploitation attempts

Patch Information

GitLab has released patched versions that address this vulnerability. Organizations should upgrade to the following versions:

• GitLab 18.9.2 - For users on the 18.9.x branch
• GitLab 18.8.6 - For users on the 18.8.x branch
• GitLab 18.7.6 - For users on the 18.7.x branch or earlier affected versions

Detailed patch information is available in the GitLab Patch Release Notes.

Workarounds

• Implement network-level rate limiting on webhook endpoints to prevent rapid exploitation attempts
• Configure web application firewalls to detect and block abnormally large webhook responses
• Restrict webhook creation and modification permissions to trusted administrative users only
• Consider implementing resource quotas at the container or VM level to limit the impact of resource exhaustion

# Example: Rate limiting webhook endpoints using nginx
# Add to your GitLab nginx configuration

limit_req_zone $binary_remote_addr zone=webhook_limit:10m rate=10r/s;

location ~ ^/api/v4/projects/.*/hooks {
    limit_req zone=webhook_limit burst=20 nodelay;
    # existing proxy configuration
}