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CVE-2026-1999— Incorrect Authorization vulnerability was identified in GitHub Enterprise Server that allowed unauthorized merging of pull requests

Quick assessment

Affected
GitHub Enterprise Server
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

GitHub Enterprise Server是美国GitHub开源的一个应用软件。提供一个将自己的GitHub实例设置为虚拟设备，从而提供可扩展，易于管理的平台。 GitHub Enterprise Server 3.19.2之前版本、3.18.5之前版本和3.17.11之前版本存在安全漏洞，该漏洞源于pull request的enable_auto_merge突变中存在授权绕过，可能导致攻击者合并自己的pull request。

AI Predicted 6.5 Difficulty: Easy EPSS 0.29% · P22

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-1999

Vulnerability Information
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Vulnerability Title
Incorrect Authorization vulnerability was identified in GitHub Enterprise Server that allowed unauthorized merging of pull requests
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:L/SC:L/SI:H/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
GitHub Enterprise Server 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
GitHub Enterprise Server是美国GitHub开源的一个应用软件。提供一个将自己的GitHub实例设置为虚拟设备，从而提供可扩展，易于管理的平台。 GitHub Enterprise Server 3.19.2之前版本、3.18.5之前版本和3.17.11之前版本存在安全漏洞，该漏洞源于pull request的enable_auto_merge突变中存在授权绕过，可能导致攻击者合并自己的pull request。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
GitHub Enterprise Server 3.17.0 ~ 3.17.11 -

II. Public POCs for CVE-2026-1999

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III. Intelligence Information for CVE-2026-1999

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Vendor Pages for CVE-2026-1999 (9)

Same Patch Batch · GitHub · 2026-02-18 · 3 CVEs total

CVE-2026-1355 Missing Authorization Check in GitHub Enterprise Server Allows Unauthorized Uploads to Rep
CVE-2026-0573 Improper Handling of HTTP Redirects vulnerability was identified in GitHub Enterprise Serv

IV. Related Vulnerabilities

Same product: Enterprise Server
Same vendor: GitHub
Same weakness: CWE-863

V. Comments for CVE-2026-1999

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