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.

CVSS 4.0

7.9CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H

CVSS 3.1

9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

0.5% chance of exploitation in the next 30 days; higher than 43% of CVEs (scores of 2026-10-26)

CWEs

CWE-436, CWE-918

Published

2026-05-07

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

Affected

• github:enterprise_server

References

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

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