Vulnerability in MessagePack (CVE-2026-48514)
Summary
Vulnerability in MessagePack (CVE-2026-48514). Risk of unauthorized operations or information disclosure. Exploitable via byteLength. Mitigation: upgrade to 3.1.7 or later.
Original description
The description as published by the source.
Summary
UnsafeBlitFormatterBase.Deserialize reads an attacker-controlled byteLength from an extension payload and allocates an array based on that value before validating it against the extension header length or remaining payload bytes.
The outer extension header is bounded by available input, but that bound is not used to constrain the inner byteLength before allocation. A very small payload can therefore request a very large T[] allocation.
Impact
Applications are affected when they deserialize untrusted payloads using Unity blit resolvers such as UnityBlitResolver or UnityBlitWithPrimitiveArrayResolver.
This is especially relevant to Unity multiplayer clients or servers that use MessagePack-CSharp for networked values such as vectors, matrices, or primitive arrays. A hostile peer can send an extension payload with a large declared byte length and cause an out-of-memory exception or process termination on memory-constrained platforms.
The resolver is opt-in, but the vulnerable value is pure wire input and the allocation happens before the formatter verifies that the declared bytes are actually present in the extension body.
Affected components
- Package:
MessagePack.UnityClient - Resolvers:
UnityBlitResolver,UnityBlitWithPrimitiveArrayResolver - API:
UnsafeBlitFormatterBase.Deserialize - Finding IDs:
MESSAGEPACKCSHARP-080, duplicate/open variantMESSAGEPACKCSHARP-OPEN-010
Patches
Fixes are prepared and will be released in coor…
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-2026-48514 has been found in MessagePack.
Attackers can target a specific entry point like byteLength 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-2026-48514" on the vendor's site.
CVE-2026-48514 (MessagePack) — CWE-770 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: byteLength / UnityBlitResolver / UnityBlitWithPrimitiveArrayResolver / MessagePack.UnityClient
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-770) exists in MessagePack. Attackers reach the vulnerable code path via byteLength without authentication.
Check the vendor advisory for the affected versions of MessagePack. Attack surface: byteLength / UnityBlitResolver / UnityBlitWithPrimitiveArrayResolver / MessagePack.UnityClient.
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
-
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。
-
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