CVE-2026-14340: An incorrect authorization vulnerability in GitHub Enterprise Server allows issue creation in unrelated public repositories
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
GitHub Enterprise Serverto a version that resolves this vulnerability.Fixed in 3.21.2 - Upgrade
Upgrade
GitHub Enterprise Serverto a version that resolves this vulnerability.Fixed in 3.20.4 - Upgrade
Upgrade
GitHub Enterprise Serverto a version that resolves this vulnerability.Fixed in 3.19.8 - Upgrade
Upgrade
GitHub Enterprise Serverto a version that resolves this vulnerability.Fixed in 3.18.11 - Upgrade
Upgrade
GitHub Enterprise Serverto a version that resolves this vulnerability.Fixed in 3.17.17 - Upgrade
Upgrade
GitHub Enterprise Serverto a version that resolves this vulnerability.Fixed in 3.16.20 - Configuration
Ensure GitHub Enterprise Server performs a repository scope check for user-to-server tokens issued by global apps so authorization verifies the token’s installation is explicitly granted access to the target repository rather than only checking installation read access.
GitHub Enterprise Server (authorization for user-to-server tokens for GitHub App installations) repository scope check for user-to-server tokens issued by global apps = add explicit repository scope check (verify token installation is explicitly granted access to target repository, not only that installation has read permissions)
Event History
Frequently Asked Questions
What is the severity of CVE-2026-14340?
CVE-2026-14340 has a medium severity rating of 5.3 based on the CVSS score.
How do I fix CVE-2026-14340?
To fix CVE-2026-14340, update your GitHub Enterprise Server to the latest version available.
What type of vulnerability is CVE-2026-14340?
CVE-2026-14340 is classified as an incorrect authorization vulnerability.
What impact does CVE-2026-14340 have on GitHub Enterprise Server?
CVE-2026-14340 allows a user to create issues in unrelated public repositories due to improper authorization checks.
Who is affected by CVE-2026-14340?
Any organization using affected versions of GitHub Enterprise Server with misconfigured token scopes may be affected by CVE-2026-14340.