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CVE-2026-54089

File Browser: Authentication Bypass via Proxy Auth Header Forgery

9.1 Critical

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Starting with 2.0.0-rc.1, when FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization. This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.61%Up 0.6 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.1

File Browser: Authentication Bypass via Proxy Auth Header Forgery

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Starting with 2.0.0-rc.1, when FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization. This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.

Record
CVE-2026-54089
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287, CWE-290
Updated
2026-11-02
EUVDEUVD-2026-39508 9.1

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Starting with 2.0.0-rc.1, when FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization. This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.

Record
EUVD-2026-39508
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-xqp3-jq6g-x3qm 9.1

File Browser: Authentication Bypass via Proxy Auth Header Forgery

Summary

When FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization.

This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.

Severity

HIGH - CVSS 3.1: 8.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)

Affected Component

  • File: auth/proxy.go, lines 21-28
  • CWE: CWE-287 (Improper Authentication), CWE-290 (Authentication Bypass by Spoofing)
  • Affected versions: All versions supporting auth.method=proxy

Prerequisite: Proxy Auth Must Be Enabled

This vulnerability is NOT exploitable on default configuration (auth.method=json). It requires the administrator to have configured proxy authentication mode. However, this is a common production deployment pattern - many organizations run FileBrowser behind a reverse proxy that handles SSO/LDAP/OAuth authentication:

  • nginx + Authelia / Authentik
  • Traefik + OAuth2 Proxy
  • Caddy + forward_auth
  • Apache + mod_auth_ldap

In these setups, the proxy authenticates the user and passes the username via HTTP header (e.g., X-Remote-User). FileBrowser trusts this header to identify the user.

| Deployment Scenario | Exploitable? | |---|---| | Default install (auth.method=json) | No — JSON auth uses password verification | | auth.method=proxy + FileBrowser only reachable via proxy (bound to 127.0.0.1 or firewalled) | No - attacker cannot reach the server directly | | auth.method=proxy + FileBrowser port exposed to network | Yes - full admin takeover |

The third scenario is common because:

  • Docker containers publish ports to 0.0.0.0 by default (e.g., -p 8085:80)
  • Administrators expose the port for debugging, monitoring, or health checks
  • Cloud deployments may have misconfigured security groups or load balancers
  • Internal networks often lack strict micro-segmentation

The core issue is that the code itself has zero defensive checks — no trusted IP validation, no shared secret, no origin verification. The entire security model relies on network-level isolation, which is fragile and not documented as a hard requirement.

Root Cause

The ProxyAuth.Auth() function unconditionally trusts the value of an HTTP request header (configured via auth.header, e.g. X-Remote-User) to determine the authenticated user's identity. There are three distinct problems in this code:

Problem 1: No Origin Validation

The function reads the header from any HTTP request regardless of source IP. It does not verify that the request originated from a trusted reverse proxy. Any client on the network can set arbitrary HTTP headers.

File: auth/proxy.go, lines 21-28:

func (a ProxyAuth) Auth(r *http.Request, usr users.Store, setting *settings.Settings, srv *settings.Server) (*users.User, error) {
    username := r.Header.Get(a.Header)  // <-- reads attacker-controlled header, no origin check
    user, err := usr.Get(srv.Root, username)
    if errors.Is(err, fberrors.ErrNotExist) {
        return a.createUser(usr, setting, srv, username)
    }
    return user, err  // <-- returns the user object, no password verification
}

There is no call to verify r.RemoteAddr against a list of trusted proxy IPs, no shared secret validation, and no signature check on the header value.

Problem 2: No…

Record
GHSA-xqp3-jq6g-x3qm
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287, CWE-290
Updated
2026-11-02
NVD 9.1

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Starting with 2.0.0-rc.1, when FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization. This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.

Record
CVE-2026-54089
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287, CWE-290
Updated
2026-11-02
OSV 9.1

File Browser: Authentication Bypass via Proxy Auth Header Forgery

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Starting with 2.0.0-rc.1, when FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization. This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.

Record
CVE-2026-54089
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287, CWE-290
Updated
2026-11-02
OSVGHSA-xqp3-jq6g-x3qm 9.1

File Browser: Authentication Bypass via Proxy Auth Header Forgery

Summary

When FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization.

This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.

Severity

HIGH - CVSS 3.1: 8.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)

Affected Component

  • File: auth/proxy.go, lines 21-28
  • CWE: CWE-287 (Improper Authentication), CWE-290 (Authentication Bypass by Spoofing)
  • Affected versions: All versions supporting auth.method=proxy

Prerequisite: Proxy Auth Must Be Enabled

This vulnerability is NOT exploitable on default configuration (auth.method=json). It requires the administrator to have configured proxy authentication mode. However, this is a common production deployment pattern - many organizations run FileBrowser behind a reverse proxy that handles SSO/LDAP/OAuth authentication:

  • nginx + Authelia / Authentik
  • Traefik + OAuth2 Proxy
  • Caddy + forward_auth
  • Apache + mod_auth_ldap

In these setups, the proxy authenticates the user and passes the username via HTTP header (e.g., X-Remote-User). FileBrowser trusts this header to identify the user.

| Deployment Scenario | Exploitable? | |---|---| | Default install (auth.method=json) | No — JSON auth uses password verification | | auth.method=proxy + FileBrowser only reachable via proxy (bound to 127.0.0.1 or firewalled) | No - attacker cannot reach the server directly | | auth.method=proxy + FileBrowser port exposed to network | Yes - full admin takeover |

The third scenario is common because:

  • Docker containers publish ports to 0.0.0.0 by default (e.g., -p 8085:80)
  • Administrators expose the port for debugging, monitoring, or health checks
  • Cloud deployments may have misconfigured security groups or load balancers
  • Internal networks often lack strict micro-segmentation

The core issue is that the code itself has zero defensive checks — no trusted IP validation, no shared secret, no origin verification. The entire security model relies on network-level isolation, which is fragile and not documented as a hard requirement.

Root Cause

The ProxyAuth.Auth() function unconditionally trusts the value of an HTTP request header (configured via auth.header, e.g. X-Remote-User) to determine the authenticated user's identity. There are three distinct problems in this code:

Problem 1: No Origin Validation

The function reads the header from any HTTP request regardless of source IP. It does not verify that the request originated from a trusted reverse proxy. Any client on the network can set arbitrary HTTP headers.

File: auth/proxy.go, lines 21-28:

func (a ProxyAuth) Auth(r *http.Request, usr users.Store, setting *settings.Settings, srv *settings.Server) (*users.User, error) {
    username := r.Header.Get(a.Header)  // <-- reads attacker-controlled header, no origin check
    user, err := usr.Get(srv.Root, username)
    if errors.Is(err, fberrors.ErrNotExist) {
        return a.createUser(usr, setting, srv, username)
    }
    return user, err  // <-- returns the user object, no password verification
}

There is no call to verify r.RemoteAddr against a list of trusted proxy IPs, no shared secret validation, and no signature check on the header value.

Problem 2: No…

Record
GHSA-xqp3-jq6g-x3qm
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287, CWE-290
Updated
2026-11-02
OSVGO-2026-5966 No score

File Browser: Authentication Bypass via Proxy Auth Header Forgery in github.com/filebrowser/filebrowser

File Browser: Authentication Bypass via Proxy Auth Header Forgery in github.com/filebrowser/filebrowser

Record
GO-2026-5966
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/filebrowser/filebrowser/v2
Go
 2.0.0-rc.1 to 2.63.18 None known
github.com/filebrowser/filebrowser
Go
 All versions None known
github.com/filebrowser/filebrowser/v2
Go
 2.0.0-rc.1 and later None known
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-54089 is a critical vulnerability (CVSS 9.1) in Filebrowser, published June 25, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.61%, the 49th percentile. No source names a fixed version.

References

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