CVE-2026-5921A 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 si…
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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
- 8.9 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L
- Weakness (CWE)
- CWE-918
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
github enterprise_server github:enterprise_server | before 3.14.26; from 3.15.0 before 3.15.21; from 3.16.0 before 3.16.17; from 3.17.0 before 3.17.14; from 3.18.0 before 3.18.8; from 3.19.0 before 3.19.5; 3.20.0 | NVD |
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
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.