CVE-2026-6736

Description

An authentication bypass vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to create a local user account, bypassing the configured external identity provider. When external authentication was enabled, the signup endpoint did not properly enforce the authentication restriction, allowing account creation and session establishment without identity provider validation. The created account was limited to the default base permissions configured on the instance. Exploitation required network access to a GHES instance configured with an external authentication provider. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.2, 3.19.6, 3.18.9, 3.17.15, and 3.16.18.

CVSS v3.1 Score

6.5

MEDIUM

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

EPSS — Exploit Prediction

0.0017

Probability of exploitation

0.38%

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-306 Missing Authentication

Affected Products

Vendor	Product	Versions
github	enterprise_server	< 3.16.18
github	enterprise_server	3.17.0 — 3.17.15
github	enterprise_server	3.18.0 — 3.18.9
github	enterprise_server	3.19.0 — 3.19.6
github	enterprise_server	3.20.0 — 3.20.2

References

Advisories & Patches

https://docs.github.com/en/[email protected]/admin/release-notes#3.16.18 https://docs.github.com/en/[email protected]/admin/release-notes#3.17.15 https://docs.github.com/en/[email protected]/admin/release-notes#3.18.9 https://docs.github.com/en/[email protected]/admin/release-notes#3.19.6 https://docs.github.com/en/[email protected]/admin/release-notes#3.20.2

Frequently Asked Questions

What is CVE-2026-6736? +

An authentication bypass vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to create a local user account, bypassing the configured external identity provider. When external authentication was enabled, the signup endpoint did not properly enforce the authentication restriction, allowing account creation and session establishment without identity provider validation. The created account was limited to the default base permissions configured on the instance. Exploitation required network access to a GHES instance configured with an external authentication provider. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.2, 3.19.6, 3.18.9, 3.17.15, and 3.16.18. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-6736? +

CVE-2026-6736 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0017, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-6736? +

CVE-2026-6736 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-2026-6736? +

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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