Atomicorp WAF Research Note: CVE-2026-54910

FileBrowser Quantum’s path traversal issue in subtitle handler allows any authenticated user to read arbitrary files

CVE Details

• Already protected by existing Atomicorp WAF rules
• Protection status: Understanding Atomicorp WAF Protection Status
• CVE: CVE-2026-54910
• Name: FileBrowser Quantum’s path traversal issue in subtitle handler allows any authenticated user to read arbitrary files
• Severity: High
• CVSS: 7.7 (v3.1) (High)
• CVSS version: 3.1
• CVSS source: GitHub_M CNA
• CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
  • Attack vector: Network
  • Attack complexity: Low
  • Privileges required: Low
  • User interaction: None
  • Scope: Changed
  • Confidentiality impact: High
  • Integrity impact: None
  • Availability impact: None
• CWE: CWE-22 — Improper Limitation of a Pathname to a Restricted Directory (‘Path Traversal’), CWE-23 — Relative Path Traversal
• Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-126 (opens in a new tab) , CAPEC-139 (opens in a new tab) , CAPEC-64 (opens in a new tab) , CAPEC-76 (opens in a new tab) , CAPEC-78 (opens in a new tab) , CAPEC-79 (opens in a new tab)
• Vendor: gtsteffaniak
• Vulnerable product: filebrowser
• CVE published: 2026-07-20
• CVE last modified: 2026-07-23
• EPSS: 0.0046; 38.6th percentile (FIRST (opens in a new tab) )
• Latest Update: 2026-09-06
• Selected Rule IDs observed: 340007 , 344360 , 347009 , 390709
• Matching rules: 4; rules with blocking actions: 4
• Would-block Rule IDs: 340007 , 344360 , 347009 , 390709
• Request surfaces inspected: JSON request data, Request URI, Request argument names, Request arguments, Request cookies, Request filename, SOAP request data, XML request data

Vulnerability Description

FileBrowser Quantum is a free, self-hosted, web-based file manager. Prior to version 1.4.3-beta, the subtitlesHandler endpoint (GET /api/media/subtitles) accepts two user-controlled query parameters: path and name, both of which are used in filesystem operations without sanitization, creating two independent path traversal vectors. The primary vector is the path parameter: it is passed directly to idx.GetRealPath() without calling SanitizeUserPath(), allowing an attacker to escape the storage root and set parentDir to any directory on the host. No existing anchor file is required. The secondary vector is the name parameter: it is joined with parentDir via filepath.Join(parentDir, name) without stripping directory components, allowing traversal relative to any resolved parentDir. Any authenticated user (regardless of role or permissions) can exploit either vector to read any text file readable by the server process, including /etc/passwd, SSH keys, database credentials, and JWT signing keys. Version 1.4.3-beta patches the issue.

Recommended Actions

1. Maintain the observed Atomicorp protections. Keep your Atomicorp commercial rules current and confirm that the selected observed rules (340007 , 344360 , 347009 , 390709 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

   • Affected versions: gtsteffaniak filebrowser version < 1.4.3-beta.
   • No specific CNA/vendor solution or workaround is included in the current CVE Record (opens in a new tab) . Review the vendor’s security advisories and supported-release guidance before making changes.

3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

• NVD (opens in a new tab)
• CVE Record (opens in a new tab)
• CVE authority reference: https://github.com/gtsteffaniak/filebrowser/commit/f3f4bbe80cb569d664174aea874d7bfa008c3b5a (opens in a new tab)
• CVE authority reference: https://github.com/gtsteffaniak/filebrowser/security/advisories/GHSA-vvp7-h4fj-m28w (opens in a new tab)

Test or Research Source

• Source: Atomicorp AI Research Framework
• Tags: cve, derived, traversal, waf-probe

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

• Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
• Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
• Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
• Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
• Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ (opens in a new tab) .