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GHSA-74m3-9qvm-rp9h

HighCVSS 8.7 / 10
Published Apr 25, 2026·Last modified May 12, 2026
Affected Components(0)

No affected components available

Description

Summary The zrok WebDAV drive backend (davServer.Dir) restricts path traversal through lexical normalization but does not prevent symlink following. When a symbolic link inside the shared DriveRoot points to a location outside that root, remote WebDAV consumers can read files and—on shares without OS-level permission restrictions—write or overwrite files anywhere on the host filesystem accessible to the zrok process.

  • Attack Vector: Network — exploitation is performed entirely over the WebDAV endpoint; the attacker issues HTTP requests to the public zrok share URL.
  • Attack Complexity: High — a precondition outside the attacker's direct control must hold: a symlink pointing outside DriveRoot must already exist within it (created locally, not via WebDAV).
  • Privileges Required: None — zrok share public --backend-mode drive exposes the WebDAV endpoint with no authentication by default.
  • User Interaction: None — once the symlink precondition is met, exploitation requires no user interaction.
  • Scope: Changed — the vulnerability allows an attacker to escape the WebDAV root (the security boundary) and access the broader host filesystem.
  • Confidentiality Impact: High — arbitrary files readable by the zrok process can be retrieved.
  • Integrity Impact: High — the WebDAV PUT handler opens files with O_RDWR|O_CREATE|O_TRUNC, meaning symlink targets outside DriveRoot can be overwritten (e.g. ~/.ssh/authorized_keys).
  • Availability Impact: None — no direct availability impact.

Affected Components

  • drives/davServer/file.go — Dir.OpenFile (line 140), Dir.Stat (line 176), Dir.Mkdir (line 133), Dir.RemoveAll (line 151)
  • endpoints/drive/backend.go — NewBackend (line 51–52)
Risk Scores
Base Score
8.7

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.

Threat Intelligence
8.0

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.33%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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