CVE-2026-1999
Authorization Bypass in GitHub Enterprise Server Enables Unauthorized PR Merge
Publication date: 2026-02-18
Last updated on: 2026-04-08
Assigner: GitHub, Inc. (Products Only)
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| github | enterprise_server | to 3.17.11 (exc) |
| github | enterprise_server | From 3.18.0 (inc) to 3.18.5 (exc) |
| github | enterprise_server | From 3.19.0 (inc) to 3.19.2 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-863 | The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. |
| CWE-918 | The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is an incorrect authorization issue in GitHub Enterprise Server. It allowed an attacker to merge their own pull request into a repository without having push access. The attacker exploited an authorization bypass in the enable_auto_merge mutation for pull requests.
The vulnerability only affected repositories that allow forking because the attack relies on opening a pull request from an attacker-controlled fork into the target repository. Exploitation was only possible under specific conditions: the pull request had to have a clean status, and the target branch could not have branch protection rules enabled.
This issue affected GitHub Enterprise Server versions prior to 3.19.2, 3.18.5, and 3.17.11, and was fixed in those versions.
How can this vulnerability impact me? :
This vulnerability can impact you by allowing an attacker to merge unauthorized code changes into your repository without having the necessary push permissions. This could lead to the introduction of malicious code, unauthorized modifications, or other security risks within your codebase.
Because the attacker can bypass normal authorization controls, it undermines the integrity of your repository and could potentially compromise your software development lifecycle.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, you should upgrade your GitHub Enterprise Server to version 3.19.2, 3.18.5, or 3.17.11 or later, as these versions contain the fix for the authorization bypass issue.
Additionally, consider enabling branch protection rules on your repositories to prevent unauthorized merges via pull requests.