CVE-2026-77987
criticalpriority · track · 39EPSS 0.009 · 59 %ileDEUSEPSS · scored 2026-10-27
A server-side request forgery (SSRF) vulnerability was identified in the notebook viewer of GitHub Enterprise Server. The notebook viewer validated the scheme and host of a user-supplied URL but did not validate the port, allowing requests to be directed to internal services listening on other ports of the same appliance. Response bodies were not returned to the requester, but response timing acted as an oracle that allowed instance secrets to be extracted character by character. An extracted secret could then be used in a separate interaction with an internal service to obtain remote code execution on the appliance. Exploitation required network access to the instance and was unauthenticated when private mode was disabled, or required any authenticated user when private mode was enabled. This vulnerability affected GitHub Enterprise Server versions 3.17 through 3.22 and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported through the GitHub Bug Bounty program.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 8.1–9.8
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (18)
Products and version ranges known to be affected.
advisories (1)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-3530Microsoft GitHub Enterprise Server: Mehrere SchwachstellenDeutsch2026-09-22csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Microsoft GitHub Enterprise Server ausnutzen, um Informationen offenzulegen, Daten zu manipulieren, beliebigen Code auszuführen oder Cross-Site-Scripting-Angriffe durchzuführen.
sources
Which sources assert this record, and when.
references (6) nvd
External citations — patches, advisories, analysis.
- https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.21Release NotesVendor Advisory
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.15Release NotesVendor Advisory
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.12Release NotesVendor Advisory
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.8Release NotesVendor Advisory
- https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.6Release NotesVendor Advisory
- https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.1Release NotesVendor Advisory
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