Use-After-Free in msgpack (CVE-2026-57585)
Summary
Vulnerability in msgpack (CVE-2026-57585). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 1.2.1 or later.
Original description
The description as published by the source.
MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is an Out-of-bounds read/crash on Unpacker reuse after a caught error, potentially leading to a DoS attack. If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV. This issue has been fixed in version 1.2.1.
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-2026-57585 has been found in msgpack.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade msgpack to 1.2.1 or later.
If unsure, ask your IT team or search "msgpack CVE-2026-57585" on the vendor's site.
CVE-2026-57585 (msgpack) — CWE-416 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 1.2.1 — 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.
Use-after-free (CWE-416) exists in msgpack.
Check the vendor advisory for the affected versions of msgpack.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.2.1.
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 'msgpack' . 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 'msgpack' . | 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
msgpack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 msgpack to 1.2.1ステージング環境で 1.2.1 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。
-
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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-57585 py3-msgpack Fixed in: 1.0.8-r0
- Debian DEBIAN-CVE-2026-57585 python-msgpack
- Ubuntu UBUNTU-CVE-2026-57585 python-pip
References
- advisory github.com
- patch github.com