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CVE-2026-1999

6.5 · MEDIUM

An incorrect authorization vulnerability was identified in GitHub Enterprise Server that allowed an attacker to merge their own pull request into a repository without having push access by exploiti…

Published Feb 18, 2026CWE-863EPSS 0.36%

Overview

CVE-2026-1999 is a medium-severity vulnerability. It was published on February 18, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

An incorrect authorization vulnerability was identified in GitHub Enterprise Server that allowed an attacker to merge their own pull request into a repository without having push access by exploiting an authorization bypass in the enable_auto_merge mutation for pull requests. This issue only affected repositories that allow forking as the attack relies on opening a pull request from an attacker-controlled fork into the target repository. Exploitation was only possible in specific scenarios. It required a clean pull request status and only applied to branches without branch protection rules enabled. This vulnerability affected GitHub Enterprise Server versions prior to 3.19.2, 3.18.5, and 3.17.11, and was fixed in versions 3.19.2, 3.18.5, and 3.17.11. This vulnerability was reported via the GitHub Bug Bounty program.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubdocs.github.com/en/[email protected]/admin/release-notes#3.17.11GitHubdocs.github.com/en/[email protected]/admin/release-notes#3.18.5GitHubdocs.github.com/en/[email protected]/admin/release-notes#3.19.2

How CyberStrike helps

Frequently asked questions

What is CVE-2026-1999?

CVE-2026-1999 is a medium-severity vulnerability. It was published on February 18, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-1999?

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-1999?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-1999?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-1999 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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