CVE-2026-77987GitHub Enterprise Server notebook viewer vulnerable to Server-side request forgery
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No exploitation reported and no EPSS estimate yet.
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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
- 9.3 CRITICAL (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- Weakness (CWE)
- CWE-918, CWE-208
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_P
- NVD analysis
- Analyzed
- Record last updated
- Sep 23, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
GitHub Enterprise Server github:enterprise_server (from the name) | from 3.17.0 before 3.17.*; fixed at 3.17.21; from 3.18.0 before 3.18.*; fixed at 3.18.15; from 3.19.0 before 3.19.*; fixed at 3.19.12; from 3.20.0 before 3.20.*; fixed at 3.20.8; from 3.21.0 before 3.21.*; fixed at 3.21.6; from 3.22.0 before 3.22.*; fixed at 3.22.1 | CNA record |
github enterprise_server github:enterprise_server | from 3.17.0 before 3.17.21; from 3.18.0 before 3.18.15; from 3.19.0 before 3.19.12; from 3.20.0 before 3.20.8; from 3.21.0 before 3.21.6; from 3.22.0 before 3.22.1 | NVD |
References
- https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.21release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.15release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.12release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.8release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.6release-notes, vendor-advisory
- https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.1release-notes, vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.