CVE-2026-8034

Summary

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.

Impact & exploitability

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

Affected products we track (1)

Recommendation

Apply the vendor fix promptly. Open any affected product above for its exact safe version.

Additional information

• NVD record
• https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.18Advisory
• https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.15Advisory
• https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.9Advisory
• https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.6Advisory
• https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.2Advisory