CVE-2026-93577: 
GitLab 脆弱性の分析と軽減

CVE-2026-93577 is a critical integer overflow vulnerability in GitLab CE/EE affecting all versions from 19.2 before 19.2.7, 19.3 before 19.3.3, and 19.4 before 19.4.1. Under certain conditions, an authenticated user can execute arbitrary code on the GitLab server by supplying a specially crafted regular expression in a CI/CD pipeline configuration. The vulnerability was published on September 24, 2026, and GitLab has released patches addressing the issue. It carries a CVSS v3.1 base score of 9.9 (Critical) (GitHub Advisory, GitLab Patch Release).

The root cause is an integer overflow or wraparound (CWE-190, mapped to CAPEC-92: Forced Integer Overflow) that occurs in the GitLab CI/CD configuration's regular expression compiler. When the compiler processes a specially crafted regex pattern, an integer value exceeds its representable range, leading to memory corruption or unexpected code execution paths. Exploitation requires only low privileges (an authenticated user with access to define or modify CI/CD configurations) and no user interaction, making it accessible to any project member who can edit .gitlab-ci.yml or equivalent pipeline configuration files. The vulnerability was originally reported via HackerOne (report #3995696) (GitHub Advisory, GitLab Issue).

Successful exploitation allows an authenticated attacker to execute arbitrary code directly on the GitLab server, resulting in full compromise of confidentiality, integrity, and availability. Because the scope is marked as "Changed," the impact can extend beyond the GitLab application itself to other components or systems accessible from the server, enabling potential lateral movement within the hosting environment. Sensitive data such as source code, secrets, tokens, and CI/CD environment variables stored on the server are at risk of exfiltration (GitHub Advisory).

As of the publication date, there is no public proof-of-concept exploit and no evidence of in-the-wild exploitation (GitHub Advisory). The EPSS score is currently 0.0, reflecting low observed exploitation probability at this time. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported. Detection support is available via Nessus plugin 349554 (Tenable).

1. Reconnaissance: Identify a GitLab CE/EE instance running versions 19.2.x before 19.2.7, 19.3.x before 19.3.3, or 19.4.x before 19.4.1. This can be done by checking the GitLab version page (/help) or HTTP response headers.
2. Obtain authentication: Log in to the GitLab instance with any valid user account that has at least Developer-level access to a project (sufficient to edit CI/CD configuration files).
3. Craft malicious regex: Construct a specially crafted regular expression designed to trigger an integer overflow in GitLab's CI/CD regex compiler. The exact pattern would exploit boundary conditions in the compiler's integer arithmetic.
4. Inject via CI/CD configuration: Commit or push a .gitlab-ci.yml file (or modify pipeline configuration via the API/UI) containing the malicious regex in a field processed by the vulnerable compiler (e.g., rules, only, or except clauses using regex matching).
5. Trigger pipeline execution: Cause the pipeline to be evaluated — this can happen automatically on push or by manually triggering a pipeline run, causing the server to compile the malicious regex.
6. Achieve code execution: The integer overflow during regex compilation results in arbitrary code execution on the GitLab server under the service account context, enabling reverse shell establishment, credential harvesting, or further lateral movement (GitHub Advisory, GitLab Patch Release).

• Logs: GitLab application logs (production.log, sidekiq.log) showing pipeline compilation errors or crashes associated with regex processing; unexpected exceptions or stack traces in the CI/CD pipeline runner logs.
• Process: Unusual child processes spawned by the GitLab Rails or Sidekiq process (e.g., /bin/bash, curl, wget, python, nc) that are not part of normal pipeline execution.
• Network: Unexpected outbound connections from the GitLab server to external IP addresses, particularly on non-standard ports, originating from the GitLab service account.
• File System: New or modified files in the GitLab installation directory, web shells, or unauthorized SSH keys added to the GitLab service account's ~/.ssh/authorized_keys.
• CI/CD Configuration: Presence of .gitlab-ci.yml files containing unusually complex or obfuscated regular expressions in rules, only, or except fields, especially recently committed by non-administrative users.

GitLab has released patched versions addressing this vulnerability: 19.2.7, 19.3.3, and 19.4.1. All GitLab CE/EE administrators running affected versions (19.2.x, 19.3.x, or 19.4.x) should upgrade immediately to the corresponding fixed release (GitLab Patch Release). As a temporary workaround prior to patching, restrict CI/CD pipeline configuration permissions to trusted users only, limiting who can create or modify .gitlab-ci.yml files and pipeline configurations. Monitor for suspicious CI/CD configuration changes and unusual server-side process activity as additional defensive measures.

Security news outlet SecurityOnline.info covered the patch release, highlighting the critical RCE nature of the vulnerability (SecurityOnline). UnderCodeNews reported on GitLab issuing a critical security patch following the discovery of two CVSS 9.9 authenticated RCE vulnerabilities (UnderCodeNews). Social media activity on Mastodon and Infosec.exchange noted the severity of the issue shortly after disclosure, reflecting community concern about the high CVSS score and the low privilege requirement for exploitation.