CVE-2026-4296 json
Incorrect Regular Expression vulnerability in GitHub Enterprise Server allowed unauthorized access to user accounts via OAuth callback URL validation bypass
published 2026-04-21 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-24545
- cvss
- 8.8
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 37%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- GitHub Enterprise Server 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5, 3.20.1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 6 mo ago
Exploit prediction
0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 7.5 | CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N |
| CNA | 4.0 | 7.5 | CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
Affected products
- GitHub Enterprise Server
Classification
- Weakness
-
- CWE-185 Incorrect Regular Expression
References
-
docs.github.com
/en/enterprise-server@3.14/admin/release-notes#3.14.26
release-notes, vendor-advisory
-
docs.github.com
/en/enterprise-server@3.15/admin/release-notes#3.15.21
release-notes, vendor-advisory
-
docs.github.com
/en/enterprise-server@3.16/admin/release-notes#3.16.17
release-notes, vendor-advisory
-
docs.github.com
/en/enterprise-server@3.17/admin/release-notes#3.17.14
release-notes, vendor-advisory
-
docs.github.com
/en/enterprise-server@3.18/admin/release-notes#3.18.8
release-notes, vendor-advisory
-
docs.github.com
/en/enterprise-server@3.19/admin/release-notes#3.19.5
release-notes, vendor-advisory
-
docs.github.com
/en/enterprise-server@3.20/admin/release-notes#3.20.1
release-notes, vendor-advisory
Sources
- CVE List CVE-2026-4296
- NVD CVE-2026-4296
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