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CVE-2026-55668 medium CVSS 6.3

Path Traversal in github.com/filebrowser/filebrowser/v2 (CVE-2026-55668)

Summary

Path traversal in github.com/filebrowser/filebrowser/v2 (CVE-2026-55668). Data can be tampered with by attackers. Exploitable via POST /api/resources/. Mitigation: upgrade to 2.63.16 or later.

Original description

The description as published by the source.

Summary

ScopedFs confines every File Browser user to a scope directory. Its within() guard is meant to reject any operation that follows a symbolic link out of that scope. When the link target does not exist yet, the guard walks up to the nearest existing ancestor and validates that instead. For a dangling symlink (target does not exist), the nearest existing ancestor is the in-scope directory containing the link, so the guard returns "in scope" and the subsequent os.OpenFile(O_CREATE) follows the link and creates the file at its out-of-scope target.

A post-auth user with Create and Modify permission can write attacker-controlled content to any non-existent path outside their scope that the File Browser process can write to. The precondition is a dangling symlink present inside the user's scope, which is the same out-of-band precondition the rest of ScopedFs is built to defend against.

This is a patch-gap variant of the GHSA-239w-m3h6-ch8v symlink confinement issue, not a resubmission of the already-published vulnerable-version behavior: GHSA-239w-m3h6-ch8v marks <= 2.63.13 vulnerable and 2.63.14 patched, while this proof reproduces on current master / v2.63.15 (be23ab3a15bf957928ecfed88de5ab67850c1b9c). The escaping-symlink-to-an-existing-target case is defended and tested. The dangling case is neither, and the gap is acknowledged in a code comment as "best-effort".

Root cause

files/scoped.go (commit be23ab3). The guard, including the mai…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-55668 has been found in github.com/filebrowser/filebrowser/v2.
Attackers can target a specific entry point like POST /api/resources/ over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 6.3/10.
What to do: upgrade github.com/filebrowser/filebrowser/v2 to 2.63.16 or later.
If unsure, ask your IT team or search "github.com/filebrowser/filebrowser/v2 CVE-2026-55668" on the vendor's site.

CVE-2026-55668 (github.com/filebrowser/filebrowser/v2) — CWE-22 / CVSS v3 6.3
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /api/resources/ / PATCH /api/tus/... / POST /api/resources/escape / ScopedFs
Patched: 2.63.16 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Path traversal (CWE-22) exists in github.com/filebrowser/filebrowser/v2. Attackers reach the vulnerable code path via POST /api/resources/.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/filebrowser/filebrowser/v2. Attack surface: POST /api/resources/ / PATCH /api/tus/... / POST /api/resources/escape / ScopedFs.

🔥 Severity

Severity: Medium (CVSS 6.3/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 2.63.16.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual POST /api/resources/ requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/filebrowser/filebrowser/v2' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'github.com/filebrowser/filebrowser/v2' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で github.com/filebrowser/filebrowser/v2 を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'POST /api/resources/' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /api/resources/ への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade github.com/filebrowser/filebrowser/v2 to 2.63.16

    ステージング環境で 2.63.16 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against POST /api/resources/ on staging to confirm patch closes the vector

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

go github.com/filebrowser/filebrowser/v2
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.63.16"}]}]
Go github.com/filebrowser/filebrowser
[{"type":"SEMVER","events":[{"introduced":"0"}]}]

References

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