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Vulnerability record · CVE-2026-1999 · published 18 February 2026

CVE-2026-1999: Github enterprise server incorrect authorization vulnerability

Github · Enterprise Server

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.

7.1 CVSS 4.0 High EPSS 0.33% · top 76.5% CWE-863 · Incorrect authorization
7.1CVSS 4.0 base score
0.33%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://docs.github.com/en/[email protected]/admin/release-notes#3.17.11
https://docs.github.com/en/[email protected]/admin/release-notes#3.18.5
https://docs.github.com/en/[email protected]/admin/release-notes#3.19.2

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-1999), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.