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CVE-2026-55495 medium CVSS 4.3

Path Traversal in github.com/cloudreve/Cloudreve/v4 (CVE-2026-55495)

Summary

Path traversal in github.com/cloudreve/Cloudreve/v4 (CVE-2026-55495). Risk of unauthorized operations or information disclosure. Exploitable via POST /api/v4/file/wopi/. Mitigation: upgrade to 4.0.0-20260613023150-7968e50429ef or later.

Original description

The description as published by the source.

Summary

Cloudreve's WOPI PUT_RELATIVE handler treats X-WOPI-SuggestedTarget as a path, not a filename. It splits the header on / and joins the segments onto the source file's directory with URI.JoinRaw, which feeds Go's url.JoinPath. url.JoinPath resolves ./.. segments, so a slash-bearing target such as a/../../evil.docx collapses to a location outside the source file's directory. The lower-level upload path then validates only the final, already-cleaned basename (evil.docx), which is harmless, and checks ownership against the resolved ancestor — which is still the same user's drive.

A WOPI access token is bound to exactly one file (the route enforces fileId == session.FileID with a 403 otherwise). PUT_RELATIVE escapes that per-file scope: a token issued for one file can create (and, conditionally, overwrite) files elsewhere in the same account.

Root cause (verified at 26b6b10)

1. Token is single-file scoped (the boundary being escaped) — middleware ViewerSessionValidation:

fileId := hashid.FromContext(c)
if fileId != session.FileID {           // 403 — token is bound to ONE file
    c.Status(http.StatusForbidden); c.Abort(); return
}

Route: wopi := noAuth.Group("file/wopi", middleware.HashID(hashid.FileID), middleware.ViewerSessionValidation()); wopi.POST(":id", controllers.ModifyFile) → POST /api/v4/file/wopi/:id?access_token=.

2. PUT_RELATIVE dispatch — routers/controllers/wopi.go:

case…

Source: GitHub Security Advisories (Global) 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-2026-55495 has been found in github.com/cloudreve/Cloudreve/v4.
Attackers can target a specific entry point like POST /api/v4/file/wopi/ over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 4.3/10.
What to do: upgrade github.com/cloudreve/Cloudreve/v4 to 4.0.0-20260613023150-7968e50429ef or later.
If unsure, ask your IT team or search "github.com/cloudreve/Cloudreve/v4 CVE-2026-55495" on the vendor's site.

CVE-2026-55495 (github.com/cloudreve/Cloudreve/v4) — CWE-22 / CVSS v3 4.3
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /api/v4/file/wopi/ / PUT_RELATIVE / URI.JoinRaw / url.JoinPath
Patched: 4.0.0-20260613023150-7968e50429ef — 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/cloudreve/Cloudreve/v4. Attackers reach the vulnerable code path via POST /api/v4/file/wopi/.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/cloudreve/Cloudreve/v4. Attack surface: POST /api/v4/file/wopi/ / PUT_RELATIVE / URI.JoinRaw / url.JoinPath.

🔥 Severity

Severity: Medium (CVSS 4.3/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 4.0.0-20260613023150-7968e50429ef.

🛡️ 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/v4/file/wopi/ requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/cloudreve/Cloudreve/v4' . 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/cloudreve/Cloudreve/v4' . | 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/cloudreve/Cloudreve/v4 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/v4/file/wopi/' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /api/v4/file/wopi/ 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/cloudreve/Cloudreve/v4 to 4.0.0-20260613023150-7968e50429ef

    ステージング環境で 4.0.0-20260613023150-7968e50429ef 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/v4/file/wopi/ 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/cloudreve/Cloudreve/v4
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.0.0-20260613023150-7968e50429ef"}]}]
go github.com/cloudreve/Cloudreve/v3
[{"type":"SEMVER","events":[{"introduced":"0"},{"last_affected":"3.0.0-20250225100611-da4e44b77af4"}]}]
Go github.com/cloudreve/Cloudreve
[{"type":"SEMVER","events":[{"introduced":"0"}]}]

References

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