CVE-2026-1999

MEDIUM

GitHub Enterprise Server - Auth Bypass

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2026-1999. PoCs published by jwde.

AI-analyzed exploit summary The repository contains minimal content with a placeholder README and a basic GitHub Actions workflow file. There is no functional exploit code or technical details related to CVE-2026-1999.

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.

Exploits (1)

nomisec STUB
by jwde · poc
https://github.com/jwde/automerge-test

The repository contains minimal content with a placeholder README and a basic GitHub Actions workflow file. There is no functional exploit code or technical details related to CVE-2026-1999.

Classification
Stub 90%
Attack Type
Other
Complexity
Trivial
Reliability
Theoretical
Target: unknown
No auth needed
devstral-2 · analyzed Mar 16, 2026 Full analysis →

Scores

CVSS v3 6.5
EPSS 0.0024
EPSS Percentile 14.1%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-863
Status published
Products (4)
GitHub/Enterprise Server 3.17.0 - 3.17.11
GitHub/Enterprise Server 3.18.0 - 3.18.5
GitHub/Enterprise Server 3.19.0 - 3.19.2
github/enterprise_server < 3.17.11
Published Feb 18, 2026
Tracked Since Feb 19, 2026