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CVE-2026-55497 medium CVSS 6.5

Vulnerability in github.com/cloudreve/Cloudreve/v4 (CVE-2026-55497)

Summary

Vulnerability in github.com/cloudreve/Cloudreve/v4 (CVE-2026-55497). Risk of unauthorized operations or information disclosure. Exploitable via PUT /api/v4/user/setting/avatar. Mitigation: upgrade to 4.0.0-20260613024411-3607f79bb44c or later.

Original description

The description as published by the source.

Summary

Cloudreve's built-in image processor decodes user-supplied images with Go's standard-library decoders (image/png, image/jpeg, image/gif) and guards only the compressed file size — never the decoded pixel dimensions. Go's decoders allocate a pixel buffer sized bytesPerPixel × width × height taken straight from the image header (e.g. a PNG's IHDR), with no upper bound on width/height. A tiny (tens-of-bytes) image that declares enormous dimensions therefore forces a multi-gigabyte-to-terabyte allocation (make([]uint8, …)), exhausting memory. The resulting out-of-memory condition is a fatal Go runtime error / kernel OOM-kill that recover() cannot catch, terminating the whole Cloudreve process for all users.

Two reachable sinks share the same root cause:

  1. Avatar upload (PUT /api/v4/user/setting/avatar) — decodes synchronously in the request handler. Any authenticated user. Cleanest single-request PoC.
  2. Thumbnail generation (built-in generator, enabled by default) — decodes in the thumbnail queue worker. Reachable for the user's own files and for files inside a share, so a planted bomb can be (re)triggered through a public share link.

Post-auth, low privilege. A single 65-byte upload deterministically takes the instance offline.

Details

Root cause — decode guarded by file size, not pixel count

The built-in generator is the default image thumbnailer:

// inventory/setting.go  @ 26b6b10
"thumb_buil…

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-2026-55497 has been found in github.com/cloudreve/Cloudreve/v4.
Attackers can target a specific entry point like PUT /api/v4/user/setting/avatar over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.5/10.
What to do: upgrade github.com/cloudreve/Cloudreve/v4 to 4.0.0-20260613024411-3607f79bb44c or later.
If unsure, ask your IT team or search "github.com/cloudreve/Cloudreve/v4 CVE-2026-55497" on the vendor's site.

CVE-2026-55497 (github.com/cloudreve/Cloudreve/v4) — CWE-400 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: PUT /api/v4/user/setting/avatar / GET /api/v4/file/thumb / width / height
Patched: 4.0.0-20260613024411-3607f79bb44c — 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

A vulnerability (CWE-400) exists in github.com/cloudreve/Cloudreve/v4. Attackers reach the vulnerable code path via PUT /api/v4/user/setting/avatar.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/cloudreve/Cloudreve/v4. Attack surface: PUT /api/v4/user/setting/avatar / GET /api/v4/file/thumb / width / height.

🔥 Severity

Severity: Medium (CVSS 6.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 4.0.0-20260613024411-3607f79bb44c.

🛡️ 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 PUT /api/v4/user/setting/avatar 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 'PUT /api/v4/user/setting/avatar' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで PUT /api/v4/user/setting/avatar 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 4.0.0-20260613024411-3607f79bb44c

    ステージング環境で 4.0.0-20260613024411-3607f79bb44c 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 PUT /api/v4/user/setting/avatar 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":"4.0.0-20260613024411-3607f79bb44c"}]}]
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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