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CVE-2026-88045 high CVSS 7.5

Vulnerability in github.com/rclone/rclone (CVE-2026-88045)

Summary

Vulnerability in github.com/rclone/rclone (CVE-2026-88045). Risk of unauthorized operations or information disclosure. Exploitable via Reserve. Mitigation: upgrade to 1.75.1 or later.

Original description

The description as published by the source.

Summary

In streamed multipart mode, serve s3 passes the request's declared part length to multipart.NewRW().Reserve(contentLength) before reading any part data. Reserve immediately obtains enough 1 MiB pool pages for the entire declared length. The request handler therefore allocates attacker-selected memory based only on Content-Length or X-Amz-Decoded-Content-Length; the client does not need to transmit the corresponding body.

--multipart-streaming-buffer-limit does not stop the allocation for the current expected part or for one oversized part when the buffer is empty. That exception is intentional to guarantee upload progress, and the flag's short help is scoped to out-of-order parts; this report therefore does not treat the option as a total memory cap. The security issue is the absence of a separate safe maximum or incremental allocation: a small request header can cause an arbitrarily large reservation and exhaust the process or host.

The default S3 configuration allows anonymous access when no auth_key is set, so an unauthenticated network client can reach the path in such deployments. Authenticated deployments require a valid S3 credential. Confirmed affected targets are v1.75.0 and development commit 5629f2668c69149bf3d9d8e2a25bb32a2648606e, both of which include streamed multipart support.

Affected Assets & Attack Surface

  • cmd/serve/s3/s3.go:40-46 defines the streaming buffer limit and describes it as a limit for out-of-order parts.…

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-2026-88045 has been found in github.com/rclone/rclone.
Attackers can target a specific entry point like Reserve over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade github.com/rclone/rclone to 1.75.1 or later.
If unsure, ask your IT team or search "github.com/rclone/rclone CVE-2026-88045" on the vendor's site.

CVE-2026-88045 (github.com/rclone/rclone) — CWE-789 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Reserve / auth_key / AuthKey / io.Copy
Patched: 1.75.1 — 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 (CWE-789) exists in github.com/rclone/rclone. Attackers reach the vulnerable code path via Reserve without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/rclone/rclone. Attack surface: Reserve / auth_key / AuthKey / io.Copy.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.75.1.

🛡️ 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 'github.com/rclone/rclone' . 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/rclone/rclone' . | 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/rclone/rclone 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
    Apply patch patch 
    Upgrade github.com/rclone/rclone to 1.75.1

    ステージング環境で 1.75.1 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を含めること。

  3. 3
    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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

go github.com/rclone/rclone
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.75.1"}]}]

References

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