Widely used GHES; authenticated admin can execute OS commands via proxy config, risk breach.
CVE-2026-4821
Authenticated GHES admin can run OS commands via proxy config.
Is CVE-2026-4821 being exploited?
Not confirmed. CVE-2026-4821 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked.
How severe is CVE-2026-4821?
CVE-2026-4821 is rated High with a CVSS score of 8.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-4821?
Yes. A fix has been recorded for CVE-2026-4821. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-4821 affect?
CVE-2026-4821 affects GitHub Enterprise Server < 3.21. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-4821?
Upgrade GHES to 3.21+ or latest patched release
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Privilege escalation: authenticated admin can execute OS commands through proxy setting injection.
Immediate action required