Overview
CVE-2025-12571 is a high-severity Denial of Service (DoS) vulnerability affecting GitLab CE/EE. This flaw allows an unauthenticated attacker to disrupt GitLab service availability by sending specifically crafted requests containing malicious JSON payloads. Successful exploitation can render the GitLab instance unusable, impacting development workflows and potentially causing data loss or corruption if not addressed promptly.
This vulnerability affects GitLab versions from 17.10 before 18.4.5, 18.5 before 18.5.3, and 18.6 before 18.6.1. Users running these versions are strongly advised to upgrade to a patched version as soon as possible.
Technical Details
The vulnerability lies in how GitLab processes incoming JSON requests. By crafting a malicious JSON payload, an attacker can trigger excessive resource consumption, leading to a Denial of Service. The specific components and code paths affected are detailed in the GitLab issue tracker (see References), but the core problem involves inefficient or unbounded processing of complex JSON structures. This means that an attacker doesn’t need any prior authentication or authorization to exploit this vulnerability, significantly increasing the risk.
The attack vector involves sending specially crafted HTTP requests to the GitLab server. The server then parses the malicious JSON payload, which causes it to consume excessive CPU, memory or other resources. This leads to the server becoming unresponsive, effectively denying service to legitimate users.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) score for CVE-2025-12571 is 7.5, categorized as HIGH severity. This score reflects the following characteristics:
- Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely over the network.
- Attack Complexity (AC): Low (L) – Exploitation requires minimal effort and expertise.
- Privileges Required (PR): None (N) – No privileges are required to exploit the vulnerability.
- User Interaction (UI): None (N) – No user interaction is required to exploit the vulnerability.
- Scope (S): Unchanged (U) – The vulnerability impacts the same system it resides on.
- Confidentiality Impact (C): None (N) – There is no impact to confidentiality.
- Integrity Impact (I): None (N) – There is no impact to data integrity.
- Availability Impact (A): High (H) – A successful exploit results in a complete denial of service.
The high availability impact, combined with the ease of exploitation and lack of required authentication, makes this a critical vulnerability to address.
Possible Impact
The potential impact of CVE-2025-12571 is significant:
- Service Disruption: GitLab instances become unavailable, halting development workflows, CI/CD pipelines, and code review processes.
- Productivity Loss: Development teams are unable to access or contribute to code, leading to project delays.
- Reputational Damage: Prolonged outages can damage the reputation of organizations relying on GitLab for software development.
- Potential Data Loss/Corruption (Indirect): While the primary impact is DoS, prolonged instability can, in some circumstances, lead to data corruption or loss.
Mitigation and Patch Steps
The primary mitigation strategy is to upgrade your GitLab instance to a patched version. The following versions are not vulnerable:
- 18.4.5 and later in the 18.4 series
- 18.5.3 and later in the 18.5 series
- 18.6.1 and later in the 18.6 series
Follow these steps to apply the patch:
- Backup Your GitLab Instance: Before applying any updates, create a complete backup of your GitLab data and configuration.
- Upgrade GitLab: Follow the official GitLab upgrade instructions for your specific installation method (e.g., Omnibus, Docker, source).
- Verify the Patch: After upgrading, verify that the new version is running and that the vulnerability has been resolved by attempting to exploit it (in a controlled environment) or checking release notes.
- Monitor for Anomalous Activity: After patching, closely monitor your GitLab instance for any unusual activity or performance issues.
If immediate patching is not possible, consider implementing temporary workarounds, such as:
- Web Application Firewall (WAF) Rules: Deploy WAF rules to filter out requests containing suspicious JSON payloads. This may require careful tuning to avoid false positives.
- Rate Limiting: Implement strict rate limiting on API endpoints to limit the number of requests from a single IP address.
Important: These workarounds are temporary measures and should not be considered a replacement for patching.
