# CVE-2026-1999: Missing authorization in Enterprise Server

> An attacker can merge pull requests into repositories without push access if branch protection is disabled and forks are allowed.

- **Severity:** High 7.1 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Feb 2026
- **Updated:** 14 Apr 2026
- **Also known as:** GHSA-qrj7-4954-7p6v

## What is CVE-2026-1999?

CVE-2026-1999 is a high-severity missing authorization vulnerability in Github Enterprise Server, published on 18 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-1999?

It affects 1 product.


Products: Github Enterprise Server.

## How do I fix CVE-2026-1999?

No fix has been published for CVE-2026-1999 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-1999 being exploited?

There is no known exploitation of CVE-2026-1999 in the wild and no public exploit code.

Public exploit code:

- Testing auto-merge CVE-2026-1999 variant (github_poc): https://github.com/jwde/automerge-test
- authz test (CVE-2026-1999 siblings) (github_poc): https://github.com/manoelprovider20-lgtm/merge-authz-test

## Other vulnerabilities in Github Enterprise Server

- [CVE-2024-4985](https://insights.sbomify.com/CVE-2024-4985/): Auth bypass in Enterprise Server (critical 10.0)
- [CVE-2022-23739](https://insights.sbomify.com/CVE-2022-23739/): Missing authorization in GitHub Enterprise Server (critical 9.8)
- [CVE-2022-46255](https://insights.sbomify.com/CVE-2022-46255/): Improper Limitation of a Pathname to a Restricted Directory in GitHub Enterprise Server leading to RCE (critical 9.8)
- [CVE-2021-22869](https://insights.sbomify.com/CVE-2021-22869/): Improper access control in GitHub Enterprise Server allows self-hosted runners to execute outside their control group (critical 9.8)
- [CVE-2024-9487](https://insights.sbomify.com/CVE-2024-9487/): Auth bypass in Enterprise Server (critical 9.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1999 and fix it if it is affected.

What it is: CVE-2026-1999 is a high-severity missing authorization vulnerability in Github Enterprise Server, published on 18 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-1999 in the wild and no public exploit code.

Affected product: Github Enterprise Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-1999/ (Markdown: https://insights.sbomify.com/CVE-2026-1999/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1999
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1999
- OSV: https://osv.dev/vulnerability/CVE-2026-1999

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1999/
Summaries are generated and may contain mistakes; the official description above is the record.