Vulnerability in github.com/cloudreve/Cloudreve/v4 (CVE-2026-77633)
Summary
Vulnerability in github.com/cloudreve/Cloudreve/v4 (CVE-2026-77633). Risk of unauthorized operations or information disclosure. Exploitable via used. Mitigation: upgrade to 4.0.0-20260715025621-7329602751c0 or later.
Original description
The description as published by the source.
Summary
Cloudreve v4 splits the storage-quota check (reading the user's used bytes and comparing them to MaxStorage) and the charge (incrementing users.storage) into two non-atomic steps in the PrepareUpload code path. This creates a Time-of-Check to Time-of-Use (TOCTOU) race condition. Any authenticated user — including an unprivileged account in the default User group — can concurrently issue several upload-session requests that all read the same stale used snapshot, each pass the check, and then each contribute their declared size to users.storage. The end result is that the total approved capacity exceeds the group's MaxStorage many times over.
The same primitive is trivially amplifiable into a storage-based denial of service. During PrepareUpload, Cloudreve reserves the declared size against users.storage before any bytes are written, so an attacker can push the reserved amount far beyond the host's physical disk (tested: a 1 GiB-quota account reserved 17 GiB in a single 20-way burst), and can then materialise the reservation by completing chunked uploads to actually write the excess bytes to disk. Amplification to the host's free space fills the disk and denies uploads for every user of the instance.
Exploitation requires only a valid session with Files.Write permission. No administrator configuration, no non-default storage policy, and no elevated privileges are needed. The default deployment (local storage policy, default User g…
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-2026-77633 has been found in github.com/cloudreve/Cloudreve/v4.
Attackers can target a specific entry point like used over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.1/10.
What to do: upgrade github.com/cloudreve/Cloudreve/v4 to 4.0.0-20260715025621-7329602751c0 or later.
If unsure, ask your IT team or search "github.com/cloudreve/Cloudreve/v4 CVE-2026-77633" on the vendor's site.
CVE-2026-77633 (github.com/cloudreve/Cloudreve/v4) — CWE-362 / CVSS v3 7.1
Attack vector: remote (network-reachable) / no user interaction
Attack surface: used / MaxStorage / users.storage / PrepareUpload
Patched: 4.0.0-20260715025621-7329602751c0 — 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.
A vulnerability (CWE-362) exists in github.com/cloudreve/Cloudreve/v4. Attackers reach the vulnerable code path via used.
Check the vendor advisory for the affected versions of github.com/cloudreve/Cloudreve/v4. Attack surface: used / MaxStorage / users.storage / PrepareUpload.
Severity: High (CVSS 7.1/10). Risk of unauthorized operations or information disclosure.
Update to 4.0.0-20260715025621-7329602751c0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. 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
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1Identify 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。 -
2Apply patch patch
Upgrade github.com/cloudreve/Cloudreve/v4 to 4.0.0-20260715025621-7329602751c0ステージング環境で 4.0.0-20260715025621-7329602751c0 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を含めること。
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3Post-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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com