Warning: Critical CVE-2026-77987 affects GitHub Enterprise Server, allowing attackers to exploit an SSRF vulnerability, potentially leading to remote code execution

GitHub Enterprise Server versions 3.17–3.22 contain a critical SSRF vulnerability (CVE-2026-77987, CVSS v4.0 9.3) in the notebook viewer that allows attacker-supplied URLs with explicit ports to reach internal services; timing-based side channels can be used to extract instance secrets and escalate to remote code execution. The advisory recommends urgent patching and increased monitoring — exploitation requires network access and may be unauthenticated when private mode is disabled.