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CVE-2026-55499 medium CVSS 4.3

Authorization Flaw in github.com/cloudreve/Cloudreve/v4 (CVE-2026-55499)

Summary

Vulnerability in github.com/cloudreve/Cloudreve/v4 (CVE-2026-55499). Risk of unauthorized operations or information disclosure. Exploitable via GET /api/v4/file/events. Mitigation: upgrade to 4.0.0-20260613030215-0b00dd308f13 or later.

Original description

The description as published by the source.

Summary

When an authenticated recipient of a single-file share opens the file event stream (GET /api/v4/file/events?uri=), Cloudreve validates the URI by listing it and then subscribes the caller to parent.ID(). For a single-file share, the share navigator resolves the bare share-root URI to the owner-side parent folder of the shared file (not the file), while the visible listing is filtered down to just the shared file. The event hub then keys topics by numeric file ID only and, on each file change, fans the event out to subscribers of every ancestor topic, filtering only the client ID that caused the event — never the subscriber's share scope.

Consequently, a recipient of one shared file can receive Server-Sent Events (type, sibling path/name, rename target, hashed file ID) for other files and subfolders in the owner's parent folder that were never shared. Contents are not disclosed; file-activity metadata is.

Details

Root cause (verified at 26b6b10)

1. Events route — authenticated, feature-flagged, no share-scope check (routers/router.go):

file := v4.Group("file"); file.Use(middleware.RequiredScopes(types.ScopeFilesRead))
file.GET("events",
    middleware.LoginRequired(),
    middleware.IsFunctionEnabled(func(c *gin.Context) bool { return dep.SettingProvider().EventHubEnabled(c) }),
    controllers.FromQuery[explorer.ExplorerEventService](...), controllers.HandleExplorerEventsPush)

EventHubEnabled defaults true (`inven…

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-2026-55499 has been found in github.com/cloudreve/Cloudreve/v4.
Attackers can target a specific entry point like GET /api/v4/file/events 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 4.0.0-20260613030215-0b00dd308f13 or later.
If unsure, ask your IT team or search "github.com/cloudreve/Cloudreve/v4 CVE-2026-55499" on the vendor's site.

CVE-2026-55499 (github.com/cloudreve/Cloudreve/v4) — CWE-863 / CVSS v3 4.3
Attack vector: remote (network-reachable) / no user interaction
Attack surface: GET /api/v4/file/events / EventHubEnabled / true / Root
Patched: 4.0.0-20260613030215-0b00dd308f13 — 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

Incorrect authorization (CWE-863) exists in github.com/cloudreve/Cloudreve/v4. Attackers reach the vulnerable code path via GET /api/v4/file/events.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/cloudreve/Cloudreve/v4. Attack surface: GET /api/v4/file/events / EventHubEnabled / true / Root.

🔥 Severity

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

🔧 How to fix

Update to 4.0.0-20260613030215-0b00dd308f13.

🛡️ 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 GET /api/v4/file/events 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 'GET /api/v4/file/events' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで GET /api/v4/file/events 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 4.0.0-20260613030215-0b00dd308f13

    ステージング環境で 4.0.0-20260613030215-0b00dd308f13 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 GET /api/v4/file/events 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":"4.0.0-20260613030215-0b00dd308f13"}]}]
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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