Vulnerability in msgpack5 (CVE-2026-107299)
Summary
Vulnerability in msgpack5 (CVE-2026-107299). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 6.1.0 or later.
Original description
The description as published by the source.
Impact
The reserved MessagePack byte 0xc1 is incorrectly treated as incomplete input. When it appears at the start of a decoder stream, all subsequent data is retained while the decoder waits for bytes that can never make the value valid, allowing memory exhaustion.
Patches
The decoder now rejects 0xc1 as invalid input. Streaming decoders release buffered input and stop after unrecoverable decoding errors.
Workarounds
Reject 0xc1 before streaming input to msgpack5, and enforce stream byte and time limits.
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-2026-107299 has been found in msgpack5.
Risk of unauthorized operations or information disclosure. CVSS score: 5.9/10.
What to do: upgrade msgpack5 to 6.1.0 or later.
If unsure, ask your IT team or search "msgpack5 CVE-2026-107299" on the vendor's site.
CVE-2026-107299 (msgpack5) — CWE-228 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 6.1.0 — apply immediately
Workaround: Reject 0xc1 before streaming input to msgpack5, and enforce stream byte and time limits.
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-228) exists in msgpack5.
Check the vendor advisory for the affected versions of msgpack5.
Severity: Medium (CVSS 5.9/10). Risk of unauthorized operations or information disclosure.
Update to 6.1.0.
Workaround: Reject 0xc1 before streaming input to msgpack5, and enforce stream byte and time limits.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'msgpack5' . 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
-
1Identify exposure identify
grep -r 'msgpack5' . | 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
msgpack5を grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Reject `0xc1` before streaming input to msgpack5, and enforce stream byte and time limits.パッチが適用されるまでの応急処置として、Reject
0xc1before streaming input to msgpack5, and enforce stream byte and time limits. を実施。回避策の副作用 (機能低下) を確認した上で。 -
3Apply patch patch
Upgrade msgpack5 to 6.1.0ステージング環境で 6.1.0 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。
-
4Post-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
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com