SSRF in GitHub Enterprise Server
CVE-2026-8034
A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook viewer that allowed an attacker to access internal services by exploiting URL parser confusion between the validation layer and the HTTP request library. The hostname validation used a different URL parser than the request library, enabling a crafted URL to pass validation while directing the request to an unintended host. Exploitation required network access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.16.18, 3.17.15, 3.18.9, 3.19.6, and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.009 (57.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 58th percentile — 57.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.009 · change: +0.003
Affected products
- GitHub Enterprise Server — versions 3.16.0, 3.17.0, 3.18.0
- GitHub Enterprise Server
Weakness classification (CWE)
References
- docs.github.com/en/enterprise-server@3.16/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.17/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.18/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.19/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
- docs.github.com/en/enterprise-server@3.20/admin/release-notes (release-notes, Release Notes, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-8034?
- CVE-2026-8034 is a critical-severity vulnerability in GitHub Enterprise Server, classified under CWE-436. CVSS score: 9.8/10. Published 2026-05-07.
- How severe is CVE-2026-8034?
- Critical severity. CVSS v3 base score is 9.8 out of 10.