CVE-2026-5921
A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.42%). 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 GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the notebook viewer followed HTTP redirects without revalidating the destination host, enabling an unauthenticated SSRF to internal services. By chaining this with regex filter queries against an internal API and measuring response time differences, an attacker could infer secret values character by character. Exploitation required that private mode be disabled and that the attacker be able to chain the instance's open redirect endpoint through an external redirect to reach internal services. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5, and 3.20.1. This vulnerability was reported via the GitHub Bug Bounty program.
- CVSS 4.0
- 8.9 HIGHCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.42% probability · 36th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-918
- Affected
- github/enterprise server
- Source
- product-cna@github.com
References
- https://docs.github.com/en/enterprise-server@3.14/admin/release-notes#3.14.26Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.21Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.17Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.14Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5Release Notes, Vendor Advisory
- https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1Release Notes, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.