Cyber Resilience

CVE-2026-35604

Access Control in Filebrowser ≤ 2.63.1

Public PoCAccess Control
Published
07 April 2026
Modified
16 April 2026
Patch / advisory
CVSS Score v4 8.2
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0033 26th percentile
Risk Priority 43 floored blend · peak EPSS

Summary

CVE-2026-35604 is a high-severity Incorrect Authorization (CWE-863) vulnerability in Filebrowser Filebrowser. Its CVSS base score is 8.2 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 26th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to AC-24 (Access Control Decisions) and AC-25 (Reference Monitor) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-35604 affects File Browser, an open-source file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. In versions prior to 2.63.1, the vulnerability arises when an administrator revokes a user's Share and Download permissions; existing share links created by that user remain fully accessible to unauthenticated users. This occurs because the public share download handler does not re-check the share owner's current permissions, classified under CWE-863 (Incorrect Authorization) with a CVSS v3.1 base score of 8.1 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N).

A low-privileged user (PR:L) with initial Share and Download permissions can exploit this by creating public share links to files before their permissions are revoked by an admin. Unauthenticated attackers who obtain these links—via phishing, social engineering, or prior sharing—can then access the shared files over the network with no user interaction required. This enables high-impact unauthorized confidentiality breaches, such as downloading sensitive files, and integrity violations, potentially including modifications depending on the share configuration.

The vulnerability is fixed in File Browser version 2.63.1, as detailed in the project's security advisory (GHSA-v9w4-gm2x-6rvf) and corresponding pull request (#5888) on GitHub. Security practitioners should upgrade to 2.63.1 or later and audit existing share links created by users whose permissions have been modified.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.1, when an admin revokes a user's Share and Download permissions, existing share links created by that user remain…

more

fully accessible to unauthenticated users. The public share download handler does not re-check the share owner's current permissions. This vulnerability is fixed in 2.63.1.

CWE(s)

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
T1548 Abuse Elevation Control Mechanism Privilege Escalation
Adversaries may circumvent mechanisms designed to control privilege elevation to gain higher-level permissions.
T1548.002 Bypass User Account Control Privilege Escalation
Adversaries may bypass UAC mechanisms to elevate process privileges on system.
T1548.003 Sudo and Sudo Caching Privilege Escalation
Adversaries may perform sudo caching and/or use the sudoers file to elevate privileges.
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-32758Same product: Filebrowser Filebrowser
CVE-2026-25890Same product: Filebrowser Filebrowser
CVE-2026-32761Same product: Filebrowser Filebrowser
CVE-2025-64523Same product: Filebrowser Filebrowser
CVE-2026-35606Same product: Filebrowser Filebrowser
CVE-2026-32759Same product: Filebrowser Filebrowser
CVE-2026-34528Same product: Filebrowser Filebrowser
CVE-2026-35607Same product: Filebrowser Filebrowser
CVE-2025-52903Same product: Filebrowser Filebrowser
CVE-2025-52995Same product: Filebrowser Filebrowser

Affected Assets

filebrowser
filebrowser
≤ 2.63.1

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

Detect
Catch it (NIST detect / respond)

Harden
Shrink the surface (DISA STIG)
  • 5 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)

Mitigating Controls (NIST 800-53 r5) AI

AC-3 directly requires correct enforcement of authorization decisions on every access request, structurally preventing incorrect checks.

AC-24 ensures access-control decisions are made and applied consistently, reducing the chance of an incorrect authorization result.

A reference monitor that is always invoked and tamper-proof forces every authorization decision through a verified, correct path.

Least-privilege assignments shrink the set of authorizations that must be checked correctly, limiting exposure to flawed checks.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-05 mostly match
prevents

Defining, enforcing, and reviewing access authorizations and least privilege directly prevents incorrect authorization checks.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

prevents

Requiring consistency between access rights and classification plus formal approval steps ensures that the authorization logic correctly distinguishes between entities that should and should not be granted access.

prevents

Enforcing policy-driven approval and role-change reviews stops incorrect or stale authorization decisions from remaining in effect after job changes or terminations.

prevents

By tying access rights to identity, device, location and classification, the control reduces the likelihood that an authorization decision will be based on an incorrect or bypassed policy.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (2 rules)
  • V-248581 OL 8 must require users to provide a password for privilege escalation. prevents CWE-863
  • V-252656 The OL 8 operating system must not be configured to bypass password requirements for privilege escalation. prevents CWE-863
RHEL 7 (1 rule)
  • V-204430 The Red Hat Enterprise Linux operating system must be configured so that users must re-authenticate for privilege escalation. prevents CWE-863
RHEL 8 (1 rule)
  • V-251712 The RHEL 8 operating system must not be configured to bypass password requirements for privilege escalation. prevents CWE-863

References