CVE-2023-6159 is a vulnerability identified in GitLab Community Edition (CE) and Enterprise Edition (EE) affecting all versions from 12.7 up to but not including 16.6.6, 16.7 up to 16.7.4, and 16.8 up to 16.8.1. The issue stems from inefficient regular expression (regex) complexity, classified under CWE-1333, which can be exploited by an attacker through a maliciously crafted Cargo.toml file. Cargo.toml is a manifest file used by Rust projects to manage dependencies and configuration. By submitting a specially designed Cargo.toml file containing regex patterns that cause excessive backtracking or complexity, an attacker can trigger a Regular Expression Denial of Service (ReDoS) condition. This leads to excessive CPU consumption on the GitLab server during processing of the file, resulting in degraded performance or complete service unavailability. The vulnerability requires network access (AV:N), low attack complexity (AC:L), and low privileges (PR:L) but no user interaction (UI:N). The scope is unchanged (S:U), and the impact is limited to availability (A:H) without affecting confidentiality or integrity. The CVSS v3.1 base score is 6.5, indicating a medium severity. No known exploits are reported in the wild yet, and no official patches are linked in the provided data, although GitLab has reserved the CVE and published the advisory. This vulnerability highlights the risks of inefficient regex handling in parsing user-supplied files, especially in widely used DevOps platforms like GitLab, which are critical for software development workflows.

For European organizations, the impact of CVE-2023-6159 can be significant, particularly for those relying heavily on GitLab for their software development lifecycle. A successful ReDoS attack can cause prolonged service outages or severe performance degradation, disrupting continuous integration/continuous deployment (CI/CD) pipelines, delaying software releases, and impacting productivity. This can be especially critical for sectors with stringent operational requirements such as finance, healthcare, and critical infrastructure, where downtime can lead to regulatory non-compliance and financial losses. Although the vulnerability does not compromise data confidentiality or integrity, the availability impact can indirectly affect business operations and trust in the development environment. Additionally, since GitLab is often integrated with other tools and services, a denial of service in GitLab may cascade to affect dependent systems. Given the medium severity and the requirement for low privileges, internal threat actors or compromised accounts could exploit this vulnerability, increasing the risk profile within organizations.

To mitigate CVE-2023-6159, European organizations should prioritize upgrading GitLab instances to the fixed versions 16.6.6, 16.7.4, or 16.8.1 or later as soon as they become available. Until patches are applied, organizations should implement strict input validation and sanitization for Cargo.toml files and other user-supplied manifests to detect and block suspicious regex patterns. Rate limiting and resource usage monitoring on GitLab servers can help detect and mitigate potential ReDoS attempts by limiting CPU consumption spikes. Restricting access to GitLab to trusted users and enforcing the principle of least privilege can reduce the risk of exploitation by low-privilege attackers. Additionally, monitoring logs for unusual processing delays or errors related to Cargo.toml parsing can provide early warning signs. Organizations should also consider isolating GitLab runners and parsing services in separate containers or virtual machines with resource quotas to contain the impact of potential ReDoS attacks. Finally, keeping abreast of GitLab security advisories and applying security patches promptly is essential.