Vulnerability in MessagePack (CVE-2026-48512)
Summary
Vulnerability in MessagePack (CVE-2026-48512). Risk of unauthorized operations or information disclosure. Exploitable via MessagePackSerializer.ConvertFromJson. Mitigation: upgrade to 3.1.7 or later.
Original description
The description as published by the source.
Summary
MessagePack-CSharp's JSON conversion helpers contain multiple recursion paths that do not consistently enforce a depth limit. These paths are in the JSON conversion component rather than normal typed MessagePack deserialization.
Three related issues are covered by this advisory:
MessagePackSerializer.ConvertFromJsonrecursively processes nested JSON arrays and objects inFromJsonCore()without consultingMessagePackSecurity.MaximumObjectGraphDepth.TinyJsonReader.ReadNextToken()recursively consumes comma and colon separator characters, allowing even malformed JSON with long separator runs to consume one stack frame per character.MessagePackSerializer.ConvertToJsonapplies depth checks to arrays and maps, but the typeless extension branch for ext-100 recursively callsToJsonCore()without applyingMessagePackSecurity.DepthStep(ref reader).
Each path can allow attacker-controlled input to exhaust the process stack and trigger an uncatchable StackOverflowException instead of failing with a catchable parse or serialization exception.
Impact
Applications are affected when they call MessagePack-CSharp JSON conversion APIs on attacker-controlled data. This includes gateways, diagnostics endpoints, migration tools, logging paths, and services that convert between external JSON and MessagePack payloads.
For JSON-to-MessagePack conversion, deeply nested JSON arrays or objects can recurse through FromJsonCore() without applying the confi…
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-2026-48512 has been found in MessagePack.
Attackers can target a specific entry point like MessagePackSerializer.ConvertFromJson over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade MessagePack to 3.1.7 or later.
If unsure, ask your IT team or search "MessagePack CVE-2026-48512" on the vendor's site.
CVE-2026-48512 (MessagePack) — CWE-674 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: MessagePackSerializer.ConvertFromJson / MessagePackSerializer.ConvertToJson / StackOverflowException / MessagePackSecurity.UntrustedData
Patched: 3.1.7 — 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-674) exists in MessagePack. Attackers reach the vulnerable code path via MessagePackSerializer.ConvertFromJson without authentication.
Check the vendor advisory for the affected versions of MessagePack. Attack surface: MessagePackSerializer.ConvertFromJson / MessagePackSerializer.ConvertToJson / StackOverflowException / MessagePackSecurity.UntrustedData.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 3.1.7.
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 'MessagePack' . 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 'MessagePack' . | 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
MessagePack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 MessagePack to 3.1.7ステージング環境で 3.1.7 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