CVE-2026-14340

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.

CVSS v3.1 Score

5.0

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.20%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
github	enterprise_server	< 3.16.20
github	enterprise_server	3.17.0 — 3.17.17
github	enterprise_server	3.18.0 — 3.18.11
github	enterprise_server	3.19.0 — 3.19.8
github	enterprise_server	3.20.0 — 3.20.4
github	enterprise_server	3.21.0 — 3.21.2

References

Other References

https://docs.github.com/en/[email protected]/admin/release-notes#3.16.20 https://docs.github.com/en/[email protected]/admin/release-notes#3.17.17 https://docs.github.com/en/[email protected]/admin/release-notes#3.18.11 https://docs.github.com/en/[email protected]/admin/release-notes#3.19.8 https://docs.github.com/en/[email protected]/admin/release-notes#3.20.4 https://docs.github.com/en/[email protected]/admin/release-notes#3.21.2

Frequently Asked Questions

What is CVE-2026-14340? +

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. It has a CVSS v3.1 base score of 5.0 (MEDIUM).

How severe is CVE-2026-14340? +

CVE-2026-14340 has a CVSS v3.1 score of 5.0 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-14340? +

CVE-2026-14340 affects products from github, specifically: enterprise_server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-14340? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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