GitLab CE/EE ReDoS via MR pre 18.9.1
CVE-2026-1388 Published on February 25, 2026
Inefficient Regular Expression Complexity in GitLab
GitLab has remediated an issue in GitLab CE/EE affecting all versions from 9.2 before 18.7.5, 18.8 before 18.8.5, and 18.9 before 18.9.1 that could have allowed an unauthenticated user to cause regular expression denial of service by sending specially crafted input to a merge request endpoint under certain conditions.
Vulnerability Analysis
CVE-2026-1388 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. An automatable proof of concept (POC) exploit exists. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is a ReDoS Vulnerability?
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles. Some regular expression engines have a feature called "backtracking". If the token cannot match, the engine "backtracks" to a position that may result in a different token that can match. Backtracking becomes a weakness if all of these conditions are met:
CVE-2026-1388 has been classified to as a ReDoS vulnerability or weakness.
Products Associated with CVE-2026-1388
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Affected Versions
GitLab:- Version 9.2 and below 18.7.5 is affected.
- Version 18.8 and below 18.8.5 is affected.
- Version 18.9 and below 18.9.1 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.