CVE-2026-1388
Published: 25 February 2026
Summary
CVE-2026-1388 is a high-severity Inefficient Regular Expression Complexity (CWE-1333) vulnerability in Gitlab Gitlab. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 16.8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2026-1388 is a regular expression denial of service (ReDoS) vulnerability, classified under CWE-1333, affecting GitLab Community Edition (CE) and Enterprise Edition (EE) in all versions from 9.2 prior to 18.7.5, 18.8 prior to 18.8.5, and 18.9 prior to 18.9.1. The issue resides in a merge request endpoint, where specially crafted input can trigger excessive resource consumption due to inefficient regular expression processing.
An unauthenticated attacker can exploit this vulnerability over the network with low complexity and no privileges by submitting malicious input to the affected merge request endpoint under certain conditions. Successful exploitation results in a denial of service, disrupting service availability with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), potentially causing significant resource exhaustion on the GitLab server.
GitLab has remediated the vulnerability through patch releases, including GitLab 18.9.1, with corresponding fixes in 18.7.5 and 18.8.5. Security practitioners should upgrade to these patched versions immediately, as detailed in the official release notes, the associated GitLab issue tracker entry, and the HackerOne disclosure report.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8721
Vulnerability details
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…
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input to a merge request endpoint under certain conditions.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
ReDoS in public merge request endpoint directly enables application-layer resource exhaustion DoS via crafted input (T1499.004).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Validates and sanitizes specially crafted inputs to the merge request endpoint to prevent ReDoS resource exhaustion.
Implements denial-of-service protections such as rate limiting to mitigate unauthenticated ReDoS attacks causing excessive CPU consumption.
Ensures timely flaw remediation by patching GitLab to vulnerable versions prior to 18.7.5, 18.8.5, or 18.9.1 to fix the inefficient regex processing.