VulnerabilityAnalyzed

CVE-2026-8034

HIGH 7.9EPSS 0.52%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.52%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

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.

CVSS 4.0: 7.9 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.52% probability · 43th percentile
CISA KEV: Not listed
Weakness: CWE-436, CWE-918
Affected: github/enterprise server
Source: product-cna@github.com

References

https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.18Release Notes, Vendor Advisory
https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.15Release Notes, Vendor Advisory
https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.9Release Notes, Vendor Advisory
https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.6Release Notes, Vendor Advisory
https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.2Release Notes, Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.