CVE-2026-77987: CWE-918 Server-Side Request Forgery (SSRF) in GitHub Enterprise Server
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.
CVE-2026-77987: CWE-918 Server-Side Request Forgery (SSRF) in GitHub Enterprise Server
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 v4.0
Score 9.3critical
Affected software
GitHub
Enterprise Server
Weaknesses
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_P
- Date Reserved
- 2026-08-21T18:51:48.052Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ab2e99cf7a7c54106c1e9a4
Added to database: 09/22/2026, 20:48:28 UTC
Last updated: 09/22/2026, 20:48:28 UTC
Views: 1
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