Vulnerability · Published Jan 19, 2026 · Assigned by GitHub_M
CVE-2026-23849File Browser vulnerable to Username Enumeration via Timing Attack in /api/login
Medium 5.3
In plain English
A medium-severity security flaw in filebrowser from filebrowser. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/filebrowser/filebrowser | no fix listed | GHSA-43mm-m3h2-3prc |
| Go | github.com/filebrowser/filebrowser | no fix listed | GO-2026-4344 |
| Go | github.com/filebrowser/filebrowser/v2 | 2.55.0 | GHSA-43mm-m3h2-3prc |
| Go | github.com/filebrowser/filebrowser/v2 | 2.55.0 | GO-2026-4344 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| filebrowser | filebrowser | < 2.55.0 |
Weakness: CWE-208 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N