Security readout for executives and security teams
Plain-English summary
CVE-2026-1388 is a GitLab denial-of-service flaw. An unauthenticated attacker could send crafted input to a merge request endpoint and trigger expensive regular expression processing, potentially making the service unavailable under certain conditions. GitLab has released fixed versions. Treat this as urgent for internet-accessible GitLab instances.
Executive priority
High priority for organizations running self-managed GitLab, because unauthenticated denial of service can disrupt software delivery. Patch promptly, especially for internet-facing instances. Business risk is service outage rather than confirmed data compromise based on available sources.
Technical view
The issue is CWE-1333, inefficient regular expression complexity, in GitLab CE/EE. It affects versions from 9.2 before 18.7.5, 18.8 before 18.8.5, and 18.9 before 18.9.1. CVSS is 7.5: network exploitable, low complexity, no privileges, no user interaction, availability impact only.
Likely exposure
Self-managed GitLab CE/EE instances in the affected version ranges are exposed if reachable over the network, especially from the internet. The source describes unauthenticated access to a merge request endpoint under certain conditions. The provided sources do not state whether GitLab.com was affected or exploited.
Exploitation context
No active exploitation is reported in the provided sources, and the CVE is not marked as KEV. Public references include a GitLab issue and HackerOne report, but both are marked permissions-required in the source bundle. The available public detail supports denial of service, not data theft or code execution.
Researcher notes
Public technical detail is limited because key GitLab and HackerOne references are permissions-restricted. The strongest public facts are the CVE description, CVSS vector, affected ranges, CWE-1333 classification, and GitLab patch release reference. Avoid assuming exploit availability or broader impact without additional vendor disclosure.
Mitigation direction
- Upgrade GitLab to 18.7.5, 18.8.5, 18.9.1, or later supported releases.
- Prioritize internet-facing GitLab instances and systems supporting critical engineering workflows.
- If immediate upgrade is delayed, limit external access to GitLab where operationally feasible.
- Monitor GitLab’s release advisory for any additional vendor guidance.
Validation and detection
- Inventory GitLab CE/EE versions across self-managed environments.
- Confirm affected instances are upgraded beyond the vulnerable version ranges.
- Review availability metrics for unusual CPU spikes or request surges around merge request endpoints.
- Confirm external exposure and access controls for GitLab web interfaces.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-1333: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-1388 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- GitLab Issue #587560CVE reference · issue-tracking, permissions-required
- HackerOne Bug Bounty Report #3482893CVE reference · technical-description, exploit
- https://about.gitlab.com/releases/2026/02/25/patch-release-gitlab-18-9-1-released/CVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Inefficient Regular Expression Complexity
Inefficient Regular Expression Complexity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.