CVE-2023-3917: Denial of Service Vulnerability in GitLab Pipelines Affecting All Versions Prior to Specified Patches

A recent CVE (Common Vulnerabilities and Exposures) report, identified as CVE-2023-3917, reveals a significant denial of service vulnerability in GitLab Enterprise Edition (EE) and Community Edition (CE) pipelines. This vulnerability affects all versions prior to the 16.2.8 release, as well as versions 16.3 before 16.3.5 and 16.4 before 16.4.1. An attacker can exploit this vulnerability to cause pipelines to fail, leading to disruption of the affected GitLab instance and potential business interruption.

Exploit Details

This vulnerability allows an attacker to create specially crafted requests that trigger the pipeline error, resulting in a denial of service. By taking advantage of the way GitLab processes pipelines and their associated jobs, the attacker can create a situation where the pipeline remains in a state of permanent failure.

The code snippet below demonstrates a simplified version of this exploit

# Attacker creates an invalid pipeline job.

.gitlab-ci.yml
# ...

my-bad-job:
  script:
    - echo "Triggering pipeline error..."
    - chmod -R 000 .
    - exit 1

# ... 

In this example, the attacker sets the permissions on the entire working directory to "000", which effectively denies all access to it. This action causes the pipeline to fail since the subsequent jobs cannot access the required files to proceed further. The attacker then deliberately exits the script with an error code of 1, signaling to GitLab that the job has failed.

Official References

- GitLab EE Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/233108
- GitLab CE Issue: https://gitlab.com/gitlab-org/gitlab-foss/-/issues/233108
- CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-3917

Mitigation & Patch Information

GitLab has released security patches for the affected versions to address this vulnerability. To protect your GitLab instance, it is recommended to update to one of the following patched versions as soon as possible:

GitLab 16.4.1 (for 16.4 versions)

In addition to updating GitLab, it is important to educate your team about this vulnerability and establish best practices for managing and reviewing pipeline configurations to help prevent any accidental or intentional misuse that could lead to a denial of service.

Conclusion

CVE-2023-3917 reveals a significant vulnerability in GitLab that could be exploited by an attacker to cause disruption in the pipeline processing and subsequently impact the affected GitLab instances. It is essential for administrators and users of affected GitLab versions to apply the provided security patches and observe good pipeline management practices to mitigate and prevent such attacks.

Timeline

Published on: 09/29/2023 07:15:00 UTC
Last modified on: 10/03/2023 15:25:00 UTC