Out-of-Bounds Read in msgpack5 (CVE-2026-107302)
Summary
Vulnerability in msgpack5 (CVE-2026-107302). Risk of unauthorized operations or information disclosure. Exploitable via map32. Mitigation: upgrade to 6.1.0 or later.
Original description
The description as published by the source.
Impact
A truncated map32 header causes an out-of-bounds buffer read and throws RangeError instead of IncompleteBufferError. Applications that rely on IncompleteBufferError to wait for additional bytes may terminate a request, stream, or worker unexpectedly. No adjacent memory is disclosed because the buffer implementation checks bounds.
Patches
The decoder now validates the complete five-byte map32 header before reading its length and reports truncated input as IncompleteBufferError.
Workarounds
Require at least five bytes before decoding a value beginning with 0xdf, or catch RangeError and treat it as incomplete input only for truncated map32 headers.
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-2026-107302 has been found in msgpack5.
Attackers can target a specific entry point like map32 over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade msgpack5 to 6.1.0 or later.
If unsure, ask your IT team or search "msgpack5 CVE-2026-107302" on the vendor's site.
CVE-2026-107302 (msgpack5) — CWE-125 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: map32 / RangeError / IncompleteBufferError
Patched: 6.1.0 — apply immediately
Workaround: Require at least five bytes before decoding a value beginning with 0xdf, or catch RangeError and treat it as incomplete input only for truncated map32 headers.
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.
Out-of-bounds read (CWE-125) exists in msgpack5. Attackers reach the vulnerable code path via map32 without authentication.
Check the vendor advisory for the affected versions of msgpack5. Attack surface: map32 / RangeError / IncompleteBufferError.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 6.1.0.
Workaround: Require at least five bytes before decoding a value beginning with 0xdf, or catch RangeError and treat it as incomplete input only for truncated map32 headers.
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
Require at least five bytes before decoding a value beginning with `0xdf`, or catch `RangeError` and treat it as incomplete input only for truncated `map32` headers.パッチが適用されるまでの応急処置として、Require at least five bytes before decoding a value beginning with
0xdf, or catchRangeErrorand treat it as incomplete input only for truncatedmap32headers. 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