Vulnerability in nextcloud (CVE-2021-43863)

Summary

vulnerability in nextcloud (CVE-2021-43863). Risk of unauthorized operations or information disclosure. Exploitable via ``FileContentProvider``. Mitigation: upgrade to `3.18.1` or later.

AI summary snake-internal / snake-material-v2

A vulnerability tracked as **CVE-2021-43863** has been found in nextcloud. Attackers can target a specific entry point like ``FileContentProvider`` over the network to misuse the product. Risk of unauthorized operations or information disclosure. CVSS score: ?/10. What to do: upgrade nextcloud to **3.18.1** or later. If unsure, ask your IT team or search "nextcloud CVE-2021-43863" on the vendor's site.

CVE-2021-43863 (nextcloud) — Attack surface: `FileContentProvider` / `DiskLruImageCacheFileProvider` Patched: `3.18.1` — 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** (unclassified) exists in nextcloud. Attackers reach the vulnerable code path via ``FileContentProvider`` without authentication.

📍 Affected scope

nextcloud — . Attack surface: `FileContentProvider` / `DiskLruImageCacheFileProvider`.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure

🔧 How to fix

Update to **3.18.1**.

🛡️ 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 request patterns matching this CVE's known IOCs. Run `grep -r 'nextcloud' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response Actions (7 steps)

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

1
Identify exposure identify
```
grep -r 'nextcloud' . | 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 `nextcloud` を grep し、稼働しているサービス・バージョンを把握する。
6
Apply patch patch
```
Upgrade nextcloud to 3.18.1
```
ステージング環境で 3.18.1 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 3 で見つけた異常検知の続報チェックを含めること。
7
Post-deployment verification verify
```
Confirm patched version is live in production
```
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 3 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

Bitnami nextcloud

[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.18.1"}]}]