Unauthenticated remote path-traversal in widely used GitHub Enterprise Server can delete repos and user storage, causing major data loss and service disruption across organizations.
CVE-2026-17556
Unauthenticated path traversal deletes files on GitHub Enterprise Server (<3.22).
Is CVE-2026-17556 being exploited?
Not confirmed. CVE-2026-17556 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. EPSS currently estimates a 0.50% probability of exploitation in the next 30 days.
How severe is CVE-2026-17556?
CVE-2026-17556 is rated High with a CVSS score of 8.8. 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-2026-17556?
Yes. A fix has been recorded for CVE-2026-17556. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-17556 affect?
CVE-2026-17556 affects GitHub Enterprise Server < 3.22, Fixed in 3.21.4, Fixed in 3.20.6, Fixed in 3.19.10, and 2 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-17556?
Upgrade to listed patched versions, restrict network access to instances, and validate backups
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote unauthenticated attacker can delete arbitrary files/directories including user storage, Git LFS, release assets and avatars, causing data loss and outage.
Immediate action required
- affected>= 3.17.0 and <= 3.17.18
- affected>= 3.18.0 and <= 3.18.12
- affected>= 3.19.0 and <= 3.19.9
- affected>= 3.20.0 and <= 3.20.5
- affected>= 3.21.0 and <= 3.21.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.