CVE-2026-77987GitHub Enterprise Server notebook viewer vulnerable to Server-side request forgery
- 9.3CriticalCVSS base score
- 0.88%Exploitation in 30 daysEPSS · top 40% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By GitHub_P
- 32 days later
· 32 days later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_PCNA (assigner) | 4.0 | Critical9.3 | 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 |
| NVDNVD · Analyzed | 4.0 | Critical9.3 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.88% · top 40% of all CVEs (14 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.3.
Affected products
- affected 3.17.0 – < 3.17.*
- affected 3.18.0 – < 3.18.*
- affected 3.19.0 – < 3.19.*
- affected 3.20.0 – < 3.20.*
- affected 3.21.0 – < 3.21.*
- affected 3.22.0 – < 3.22.*
References
References6
- https://docs.github.com/en/[email protected]/admin/release-notes#3.17.21 (opens in a new tab)release-notes
- https://docs.github.com/en/[email protected]/admin/release-notes#3.18.15 (opens in a new tab)release-notes
- https://docs.github.com/en/[email protected]/admin/release-notes#3.19.12 (opens in a new tab)release-notes
- https://docs.github.com/en/[email protected]/admin/release-notes#3.20.8 (opens in a new tab)release-notes
- https://docs.github.com/en/[email protected]/admin/release-notes#3.21.6 (opens in a new tab)release-notes
- https://docs.github.com/en/[email protected]/admin/release-notes#3.22.1 (opens in a new tab)release-notes
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-84872 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-77987)Record last updated .