CVE-2026-1662: GitLab CE/EE DoS Vulnerability

CVE-2026-1662 Overview

CVE-2026-1662 is a Denial of Service vulnerability affecting GitLab Community Edition (CE) and Enterprise Edition (EE). The vulnerability exists in the Jira events endpoint and allows an unauthenticated attacker to cause service disruption by sending specially crafted requests. This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling), indicating that the affected endpoint lacks proper resource management controls.

Critical Impact

Unauthenticated attackers can remotely disrupt GitLab services by exploiting the Jira integration endpoint, potentially causing significant availability issues for organizations relying on GitLab for their development workflows.

Affected Products

• GitLab CE/EE versions 14.4 through 18.7.4
• GitLab CE/EE versions 18.8 through 18.8.4
• GitLab CE/EE versions 18.9.0

Discovery Timeline

• 2026-02-25 - CVE-2026-1662 published to NVD
• 2026-02-25 - GitLab releases security patch (versions 18.7.5, 18.8.5, and 18.9.1)
• 2026-02-25 - Last updated in NVD database

Technical Details for CVE-2026-1662

Vulnerability Analysis

This vulnerability stems from inadequate resource allocation controls in GitLab's Jira events endpoint. The affected component fails to properly limit or throttle incoming requests, which can be exploited by an unauthenticated user to exhaust server resources. The attack can be executed remotely over the network without requiring any user interaction or authentication credentials.

The Jira integration feature in GitLab allows synchronization between Jira issues and GitLab, with the events endpoint serving as the receiver for Jira webhooks. When specially crafted requests are sent to this endpoint, the server allocates resources without proper bounds checking, leading to resource exhaustion and subsequent denial of service conditions.

Root Cause

The root cause is CWE-770: Allocation of Resources Without Limits or Throttling. The Jira events endpoint in GitLab does not implement sufficient rate limiting or resource allocation controls, allowing attackers to overwhelm the service with malicious requests. This architectural weakness enables resource exhaustion attacks that can render the GitLab instance unavailable to legitimate users.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a vulnerable GitLab instance with Jira integration enabled
2. Crafting malicious HTTP requests targeting the Jira events endpoint
3. Sending a high volume of these specially crafted requests to exhaust server resources
4. Causing the GitLab service to become unresponsive or crash

The attack surface is exposed through the web interface, making any internet-facing GitLab instance with Jira integration a potential target. For detailed technical information about the exploit mechanism, refer to the HackerOne Vulnerability Report #3519694 and the GitLab Issue #588206 Discussion.

Detection Methods for CVE-2026-1662

Indicators of Compromise

• Unusual spike in HTTP requests to the Jira events endpoint (/api/v4/integrations/jira/events or similar paths)
• Server resource exhaustion symptoms including high CPU utilization, memory consumption, or connection pool depletion
• Multiple requests from single IP addresses or unusual geographic locations targeting Jira-related endpoints
• GitLab application logs showing repeated Jira event processing errors or timeouts

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block abnormal request patterns to Jira integration endpoints
• Configure rate limiting alerts on GitLab reverse proxy or load balancer to identify potential DoS attempts
• Monitor GitLab application logs for excessive Jira event processing activity or error patterns
• Deploy network intrusion detection systems (IDS) with signatures for GitLab DoS attack patterns

Monitoring Recommendations

• Set up alerting thresholds for HTTP request rates to GitLab API endpoints, particularly those related to Jira integration
• Monitor system resource utilization (CPU, memory, network connections) for anomalous spikes
• Implement centralized logging to correlate events across GitLab instances and identify coordinated attacks
• Conduct regular security assessments of GitLab instances to verify proper rate limiting configurations

How to Mitigate CVE-2026-1662

Immediate Actions Required

• Upgrade GitLab CE/EE to patched versions: 18.7.5, 18.8.5, or 18.9.1 immediately
• If immediate patching is not possible, consider temporarily disabling the Jira integration until the update can be applied
• Implement network-level rate limiting for requests to GitLab's Jira events endpoint
• Review access logs to determine if exploitation attempts have already occurred

Patch Information

GitLab has released patched versions that address this vulnerability. Organizations should upgrade to the following versions based on their current deployment:

For complete patch details and upgrade instructions, see the GitLab Release Patch Announcement.

Workarounds

• Deploy a reverse proxy or WAF with rate limiting rules specifically targeting the Jira events endpoint
• Restrict network access to the Jira integration endpoint to known Jira server IP addresses only
• Temporarily disable the Jira integration feature if not critical to operations until patching is complete
• Implement IP-based access control lists (ACLs) to limit which sources can access GitLab's integration endpoints

# Example nginx rate limiting configuration for GitLab Jira endpoint
# Add to nginx configuration file

# Define rate limiting zone
limit_req_zone $binary_remote_addr zone=jira_events:10m rate=10r/s;

# Apply rate limiting to Jira events endpoint
location ~ ^/api/v4/integrations/jira {
    limit_req zone=jira_events burst=20 nodelay;
    limit_req_status 429;
    proxy_pass http://gitlab-workhorse;
}