Path Traversal in GitHub Enterprise Server
CVE-2026-17556
A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS objects, release assets, attachments, and avatars. The X-GitHub-Request-Id request header was used without sanitization as a filesystem path segment for the upload buffer directory, so a traversal value pointed the buffer at an arbitrary path and the deferred cleanup routine recursively removed the traversed target. Exploitation required only network reachability to the instance and no authentication, and it worked even when private mode was enabled. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.4, 3.20.6, 3.19.10, 3.18.13 and 3.17.19. This vulnerability was reported via the GitHub Bug Bounty program.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H.
EPSS exploit prediction
EPSS: 0.008 (56.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 56.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000
Affected products
- GitHub Enterprise Server — versions 3.17.0, 3.18.0, 3.19.0
- GitHub Enterprise Server
Weakness classification (CWE)
References
- docs.github.com/en/enterprise-server@3.17/admin/release-notes (release-notes, Product, Release Notes)
- docs.github.com/en/enterprise-server@3.18/admin/release-notes (release-notes, Product, Release Notes)
- docs.github.com/en/enterprise-server@3.19/admin/release-notes (release-notes, Product, Release Notes)
- docs.github.com/en/enterprise-server@3.20/admin/release-notes (release-notes, Product, Release Notes)
- docs.github.com/en/enterprise-server@3.21/admin/release-notes (release-notes, Product, Release Notes)
Frequently asked questions
- What is CVE-2026-17556?
- CVE-2026-17556 is a critical-severity vulnerability in GitHub Enterprise Server, classified under Path Traversal. CVSS score: 9.1/10. Published 2026-08-05.
- How severe is CVE-2026-17556?
- Critical severity. CVSS v3 base score is 9.1 out of 10.