CVE-2026-17556

HIGH CVSS 4.0: 8.8 EPSS 0.50%
Updated Aug 18, 2026
GitHub
Parameter Value
CVSS 8.8 (HIGH)
Affected Versions 3.18.0 — 3.21.4
Fixed In 3.17.19
Type CWE-22 (Path Traversal)
Vendor GitHub
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service

CVSS Vector v4.0

Weakness Type (CWE)

Vulnerable Products 5

Configuration From (including) Up to (excluding)
Github Enterprise_Server
cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*
3.17.19
Github Enterprise_Server
cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*
3.18.0 3.18.13
Github Enterprise_Server
cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*
3.19.0 3.19.10
Github Enterprise_Server
cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*
3.20.0 3.20.6
Github Enterprise_Server
cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*
3.21.0 3.21.4