CVE-2026-77987 GitHub Enterprise Server notebook viewer vulnerable to Server-side request forgery
Attacker can exploit SSRF in notebook viewer to extract secrets and achieve remote code execution on GitHub Enterprise Server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-77987?
CVE-2026-77987 is a critical server-side request forgery vulnerability in Github Enterprise Server, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-77987?
It affects 1 product.
Products include Github Enterprise Server.
How do I fix CVE-2026-77987?
No fix has been published for CVE-2026-77987 yet. Limit exposure of the affected software until one is available.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-77987 being exploited?
There is no known exploitation of CVE-2026-77987 in the wild and no public exploit code.
Other vulnerabilities in Github Enterprise Server
- CVE-2024-4985 Auth bypass in Enterprise Server
- CVE-2022-23739 Missing authorization in GitHub Enterprise Server
- CVE-2022-46255 Improper Limitation of a Pathname to a Restricted Directory in GitHub Enterprise Server leading to RCE
- CVE-2021-22869 Improper access control in GitHub Enterprise Server allows self-hosted runners to execute outside their control group
- CVE-2024-9487 Auth bypass in Enterprise Server
Sources
Also known as GHSA-5p5v-w43x-q8v7.