Cyber Resilience

CVE-2026-23849

Filebrowser ≤ 2.55.0

Public PoC
Published
19 January 2026
Modified
03 February 2026
Patch / advisory
View advisory
CVSS Score v3.1 5.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS Score 0.0042 35th percentile
Risk Priority 44 floored blend · peak EPSS

Summary

CVE-2026-23849 is a medium-severity Observable Timing Discrepancy (CWE-208) vulnerability in Filebrowser Filebrowser. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Password Guessing (T1110.001); ranked at the 35th 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 IA-6 (Authentication Feedback) and SA-11 (Developer Testing and Evaluation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

File Browser provides a file managing interface within a specified directory and can be used to upload, delete, preview, rename, and edit files. Prior to version 2.55.0, the JSONAuth. Auth function contains a logic flaw that allows unauthenticated attackers to…

more

enumerate valid usernames by measuring the response time of the /api/login endpoint. The vulnerability exists due to a "short-circuit" evaluation in the authentication logic. When a username is not found in the database, the function returns immediately. However, if the username does exist, the code proceeds to verify the password using bcrypt (users.CheckPwd), which is a computationally expensive operation designed to be slow. This difference in execution path creates a measurable timing discrepancy. Version 2.55.0 contains a patch for the issue.

CWE(s)
CWE-208CWE-203

Related Threats

MITRE ATT&CK Enterprise Techniques

T1110.001 Password Guessing Credential Access
Adversaries with no prior knowledge of legitimate credentials within the system or environment may guess passwords to attempt access to accounts.
attack.mitre.org →
T1087 Account Discovery Discovery
Adversaries may attempt to get a listing of valid accounts, usernames, or email addresses on a system or within a compromised environment.
attack.mitre.org →
T1087.001 Local Account Discovery
Adversaries may attempt to get a listing of local system accounts.
attack.mitre.org →
T1087.002 Domain Account Discovery
Adversaries may attempt to get a listing of domain accounts.
attack.mitre.org →
T1087.003 Email Account Discovery
Adversaries may attempt to get a listing of email addresses and accounts.
attack.mitre.org →
T1087.004 Cloud Account Discovery
Adversaries may attempt to get a listing of cloud accounts.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-52997Same product: Filebrowser Filebrowser
CVE-2026-28492Same product: Filebrowser Filebrowser
CVE-2026-30933Same product: Filebrowser Filebrowser
CVE-2025-52996Same product: Filebrowser Filebrowser
CVE-2025-52995Same product: Filebrowser Filebrowser
CVE-2025-64523Same product: Filebrowser Filebrowser
CVE-2026-35607Same product: Filebrowser Filebrowser
CVE-2025-52900Same product: Filebrowser Filebrowser
CVE-2026-35604Same product: Filebrowser Filebrowser
CVE-2026-35605Same product: Filebrowser Filebrowser

Affected Assets

filebrowser
filebrowser
≤ 2.55.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 1 hardening rule · 1 OS baseline
Validate
Prove the fix (OWASP ASVS)
  • V11.2.4

Mitigating Controls (NIST 800-53 r5) AI

IA-6 Authentication Feedback good match

Obscures authentication feedback so that success/failure differences are not observable to attackers.

SA-11 Developer Testing and Evaluation good match

Developer testing can include timing analysis or side-channel test cases that reveal observable timing discrepancies.

SI-11 Error Handling good match

Requires error messages to avoid revealing exploitable details, directly stopping observable response discrepancies.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles can mandate constant-time algorithms and side-channel resistance so timing discrepancies are never introduced.

SC-13 Cryptographic Protection partial match

Requiring approved cryptographic modules and algorithms implicitly demands implementations free of observable timing leaks.

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.PS-06 mostly match
prevents

Secure SDLC practices directly require constant-time implementations that eliminate observable timing discrepancies.

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.

A.8.17 Clock synchronization none match
none

Consistent reference clocks limit the attacker's ability to measure or manipulate timing differences that could reveal internal state or processing paths.

References