CVE-2026-4296

Description

An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application's registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized access to the victim's account with the scopes granted to the OAuth application. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS v3.1 Score

8.8

HIGH

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

EPSS — Exploit Prediction

0.0004

Probability of exploitation

0.13%

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-185 CWE-185

Affected Products

Vendor	Product	Versions
github	enterprise_server	< 3.14.26
github	enterprise_server	3.15.0 — 3.15.21
github	enterprise_server	3.16.0 — 3.16.17
github	enterprise_server	3.17.0 — 3.17.14
github	enterprise_server	3.18.0 — 3.18.8
github	enterprise_server	3.19.0 — 3.19.5
github	enterprise_server	All

References

Advisories & Patches

https://docs.github.com/en/[email protected]/admin/release-notes#3.14.26 https://docs.github.com/en/[email protected]/admin/release-notes#3.15.21 https://docs.github.com/en/[email protected]/admin/release-notes#3.16.17 https://docs.github.com/en/[email protected]/admin/release-notes#3.17.14 https://docs.github.com/en/[email protected]/admin/release-notes#3.18.8 https://docs.github.com/en/[email protected]/admin/release-notes#3.19.5 https://docs.github.com/en/[email protected]/admin/release-notes#3.20.1

Frequently Asked Questions

What is CVE-2026-4296? +

An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application's registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized access to the victim's account with the scopes granted to the OAuth application. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program. It has a CVSS v3.1 base score of 8.8 (HIGH).

How severe is CVE-2026-4296? +

CVE-2026-4296 has a CVSS v3.1 score of 8.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0004, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-4296? +

CVE-2026-4296 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-2026-4296? +

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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