# 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 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.

- **CVSS:** 8.9
- **EPSS:** 0.1%
- **CWE:** CWE-918

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-5921
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