Medium severity · published Feb 18, 2026
CVE-2026-1999
Incorrect Authorization vulnerability was identified in GitHub Enterprise Server that allowed unauthorized merging of pull requests
6.5
CVSS
0.4%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 30% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ES
Enterprise Server · GitHub
3.17.0 before 3.17.11; 3.18.0 before 3.18.5; 3.19.0 before 3.19.2 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-1999
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-1999
docs.github.com
https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.11
docs.github.com
https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.5
docs.github.com
https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.2
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