CVE-2026-77987
A server-side request forgery (SSRF) vulnerability was identified in the notebook viewer of GitHub Enterprise Server.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.88%). 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 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 4.0
- 9.3 CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.88% probability · 59th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-208, CWE-918
- Affected
- github/enterprise server
- Source
- product-cna@github.com
EPSS moved from 0.9% on 23 September 2026 to 0.9% on 26 October 2026.
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.