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CVE-2026-48777 gtsteffaniak CVE debrief

CVE-2026-48777 is a critical vulnerability in FileBrowser Quantum, a free, self-hosted, web-based file manager. Versions prior to 1.3.2-stable, 1.4.0-beta, and 1.4.1-beta are vulnerable to Path Traversal through the publicPatchHandler in backend/http/public.go. This vulnerability allows an attacker to move, copy, or rename arbitrary files within the share owner's source root by exploiting a public share link with AllowModify=true.

Vendor
gtsteffaniak
Product
filebrowser
CVSS
CRITICAL 9.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-16
Original CVE updated
2026-06-17
Advisory published
2026-06-16
Advisory updated
2026-06-17

Who should care

Users of FileBrowser Quantum versions prior to 1.3.3-stable and 1.4.2-beta should update to the latest version to prevent exploitation of this vulnerability.

Technical summary

The vulnerability is caused by the publicPatchHandler in backend/http/public.go joining user-controlled fromPath and toPath body fields with the trusted d.share.Path before the downstream sanitizer runs. This allows an attacker to traverse the file system and access files outside the shared directory.

Defensive priority

High

Recommended defensive actions

  • Update to FileBrowser Quantum version 1.3.3-stable or 1.4.2-beta or later.
  • Restrict access to public share links with AllowModify=true.
  • Monitor file system activity for suspicious behavior.

Evidence notes

This vulnerability has been fixed in versions 1.3.3-stable and 1.4.2-beta. References: [ref-4](https://github.com/gtsteffaniak/filebrowser/releases/tag/v1.3.3-stable), [ref-5](https://github.com/gtsteffaniak/filebrowser/releases/tag/v1.4.2-beta), [ref-6](https://github.com/gtsteffaniak/filebrowser/security/advisories/GHSA-qqqm-5547-774x).

Sources and references

Verified primary and authoritative sources

  • CVE-2026-48777 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-48777

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-48777 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-48777

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.