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CVE-2026-91144 – Authorization Bypass / Arbitrary File Download – ZFile ≤ 5.0.5

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Summary

CVE-2026-91144 is an authorization bypass vulnerability in ZFile, an open-source online file management/cloud storage system, affecting all versions through 5.0.5. The flaw resides in the share-link download endpoint, which fails to validate requested file paths against the set of entries a share link is actually permitted to expose. Because the vulnerability requires no authentication beyond possession of a valid share link and is remotely exploitable over the network, it carries a high severity rating.

Technical details

  • Root cause: The download endpoint’s server-side logic (ShareLinkFileService) does not verify that a requested file path falls within the set of files/folders explicitly authorized under a given share link before serving the file.
  • Trigger conditions: An attacker must possess (or obtain) a valid, active share link generated by a legitimate ZFile user; no additional credentials or privileges are required.
  • Attack vector: Network-based (remote, unauthenticated relative to the target file) — the attacker manipulates request/query parameters on the download endpoint to reference file paths outside the entries the share link was intended to expose, while still remaining within the shared base directory.
  • Impact: Unauthorized disclosure/download of arbitrary files located within the shared base directory that were not intended to be included in the share, resulting in a confidentiality breach. No indication of impact to integrity or availability.

Affected software

  • ZFile versions 0 through 5.0.5 (all releases up to and including 5.0.5)

Severity

  • CVSS v3.1 Base Score: 7.5 (High) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
  • CVSS v4.0 Base Score: 8.7 (High) — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade ZFile to a version newer than 5.0.5 that enforces server-side validation of requested file paths against the allowed entries of a share link. Consult the official ZFile GitHub repository for the latest release before deploying.
  • If no patch is available: Disable or restrict the share-link feature until a fix is applied; audit and revoke existing share links, especially those pointing to directories containing sensitive files; restrict network exposure of ZFile instances (e.g., place behind authentication proxies or VPN) to limit access to the download endpoint; monitor access logs for anomalous download requests referencing unexpected file paths under shared directories.

References

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