# CVE-2026-4296: Incorrect Regular Expression vulnerability in GitHub Enterprise Server allowed unauthorized access to user accounts via OAuth callback URL validation bypass

> CVE-2026-4296: Incorrect Regular Expression vulnerability in GitHub Enterprise Server allowed unauthorized access to user accounts via OAuth callback URL validation bypass. CVSS 8.8 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-4296
Last updated: 2026-06-17T10:56:22Z

- Published: 2026-04-21 22:12 UTC · Updated: 2026-06-17 10:56 UTC · Assigner: GitHub\_P
- CVSS: 8.8 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- EPSS: 0.43%, 37th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-185

## 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.

## Affected vendors and products

- GitHub: Enterprise Server

## Tracked companies

- [GitHub](https://rewindex.com/company/github.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-4296)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-4296)
- [https://docs.github.com/en/enterprise-server@3.14/admin/release-notes\#3.14.26](https://docs.github.com/en/enterprise-server@3.14/admin/release-notes#3.14.26)
- [https://docs.github.com/en/enterprise-server@3.15/admin/release-notes\#3.15.21](https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.21)
- [https://docs.github.com/en/enterprise-server@3.16/admin/release-notes\#3.16.17](https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.17)
- [https://docs.github.com/en/enterprise-server@3.17/admin/release-notes\#3.17.14](https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.14)
- [https://docs.github.com/en/enterprise-server@3.18/admin/release-notes\#3.18.8](https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8)
- [https://docs.github.com/en/enterprise-server@3.19/admin/release-notes\#3.19.5](https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5)
- [https://docs.github.com/en/enterprise-server@3.20/admin/release-notes\#3.20.1](https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1)

---

_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


---
Canonical: https://rewindex.com/cve/CVE-2026-4296 · Markdown: https://rewindex.com/cve/CVE-2026-4296.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-4296 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:09:54.640Z