Quadratic parsing in msgpack5 streaming decoder blocks the event loop
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-407.
Summary
msgpack5 versions before 6.1.0 for node.js and the browser have a streaming decoder that reparses an incomplete array or map from the beginning whenever another chunk arrives (CWE-407). A remote peer can split one valid MessagePack container into many small chunks, causing completed elements to be decoded repeatedly. This produces quadratic CPU use that blocks the event loop.
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
Description from the CNA
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| mcollina | msgpack5 | before 6.1.0 | 6.1.0 | Patch available | CNA |
| — | msgpack5 (npm) | before 6.1.0 | 6.1.0 | Patch available | GHSA-gcx5-hxj7-gpqq |
- msgpack5 Vendormcollina Affected before 6.1.0 Fixed in 6.1.0 Patch available CNA
- msgpack5 (npm) Vendor— Affected before 6.1.0 Fixed in 6.1.0 Patch available GHSA-gcx5-hxj7-gpqq
Remediation
Upgrade the npm package msgpack5 to version 6.1.0, which fixes this issue.
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
- Fix · CNA msgpack5 (mcollina) Fixed in 6.1.0
- Fix · GHSA-gcx5-hxj7-gpqq msgpack5 (npm) Fixed in 6.1.0 Advisory →
Timeline
- 2026-10-08 Threatist record created from CVE-2026-107297
- 2026-10-08 Alias added: GHSA-gcx5-hxj7-gpqq
References
More mcollina vulnerabilities
- TI-2026-76780 Command injection in mcollina mcp-ripgrep Advanced Search Tool CVSS 4.0MEDIUM 4.8
- TI-2026-69605 Truncated map32 headers throw RangeError in msgpack5 decoder CVSS 3.1HIGH 7.5
- TI-2026-69603 msgpack5 streaming decoder recursion can exhaust the call stack CVSS 3.1HIGH 7.5
- TI-2026-69599 Deeply nested input exhausts the stack in msgpack5 decoder CVSS 3.1MEDIUM 5.3
- TI-2026-69606 Prototype pollution in msgpack5 with partial options CVSS 3.1MEDIUM 6.5
- TI-2026-69600 Reserved byte in msgpack5 causes unbounded stream buffering CVSS 3.1MEDIUM 5.9
Sources
- CVE-2026-107297 · CVE Program
- CVE-2026-107297 · NVD
- FIRST EPSS
- GHSA-gcx5-hxj7-gpqq · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences