CVE-2026-1500: GitLab Authenticated Denial of Service via Malicious File Upload

Technical summary

CVE-2026-1500 is an uncontrolled resource consumption flaw (CWE-770) in GitLab's file upload handling mechanism. During the processing of certain file types or structures, the application fails to enforce resource quotas or timeout controls, allowing an authenticated attacker to exhaust system capacity. The vulnerability affects all instances of GitLab Community Edition and Enterprise Edition running version 17.10 through 18.10.7, 18.11 through 18.11.4, and 19.0 through 19.0.1. The CVSS 3.1 score of 6.5 reflects a network-accessible service with low attack complexity, requiring valid authentication, and resulting in high availability impact with no confidentiality or integrity compromise.

Business impact

An attacker with valid GitLab credentials can repeatedly upload malicious files to degrade or fully disable GitLab services, blocking all users from accessing repositories, CI/CD pipelines, and project management features. For organizations relying on GitLab as a critical development infrastructure component, this creates operational disruption and potential supply chain delays. The attack requires no advanced techniques and could be executed by a disgruntled employee, contractor, or account holder with compromised credentials.

Affected systems

All GitLab Community Edition (CE) and Enterprise Edition (EE) installations are affected if running: version 17.10 or later but earlier than 18.10.8; version 18.11.0 through 18.11.4; or version 19.0.0 and 19.0.1. Patch releases 18.10.8, 18.11.5, and 19.0.2 or later contain the remediation. Verify your installed version in the GitLab admin dashboard under Settings > General.

Exploitability

Exploitation is straightforward and requires only valid authentication credentials. An attacker does not need administrative privileges, advanced technical knowledge, or special tooling—a standard file upload interface and loop script suffice. However, the vulnerability is not currently tracked in CISA's Known Exploited Vulnerabilities catalog, suggesting limited public weaponization at publication time. Organizations should still assume that malicious actors monitoring GitLab security advisories will develop and test attacks rapidly.

Remediation

Upgrade immediately to GitLab 18.10.8, 18.11.5, 19.0.2, or any later release. For organizations unable to patch immediately, implement network access controls to restrict GitLab connectivity to trusted users and VPNs, monitor file upload activity for anomalies, and establish per-user upload quotas and timeouts at the application or reverse-proxy layer. Consider temporarily disabling file uploads if your workflow permits.

Patch guidance

Apply the corresponding patch version from the affected range: CE/EE 17.10 users should upgrade to 18.10.8 or later; those on 18.11 should upgrade to 18.11.5 or later; those on 19.0 should upgrade to 19.0.2 or later. GitLab patches are cumulative, so upgrading to the latest stable release within your supported tier is safe. Before patching production systems, validate in a staging environment and review GitLab's release notes for any breaking changes or required migration steps. Coordinate with your development and operations teams to schedule patching during a maintenance window.

Detection guidance

Monitor GitLab's web and API access logs for patterns of repeated file uploads from the same authenticated user, particularly within short time windows or targeting large file sizes. Track system resource metrics (CPU utilization, memory consumption, disk I/O) for sudden spikes correlated with upload activity. Configure alerts on GitLab's internal job queue and background worker logs for hung or timeout events. If you have network-level visibility, look for sustained HTTP POST requests to repository or project endpoints. After patching, baseline normal upload activity and alert on deviations.

Why prioritize this

Although assigned a MEDIUM severity score, this vulnerability warrants prompt attention because file upload is a ubiquitous feature used across development workflows, the attack requires no privilege escalation, and the impact is immediate service denial. The low attack complexity and lack of UI interaction for the attacker make it attractive to malicious insiders and opportunistic threat actors. Organizations with large user bases or high-trust credentials distribution should prioritize patching within 1–2 weeks.

Risk score, explained

The CVSS 3.1 score of 6.5 reflects: (1) network accessibility (AV:N), making the vulnerability remotely triggerable; (2) low attack complexity (AC:L), requiring no special conditions; (3) low privilege requirement (PR:L), exploitable by any authenticated user; (4) no user interaction (UI:N); (5) unchanged scope (S:U); and (6) high availability impact (A:H), causing denial of service. The absence of confidentiality or integrity impact prevents a higher score, but the ease of exploitation and service disruption justify prompt remediation.

Frequently asked questions