Quick answers
- Is CVE-2026-107297 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-107297 being exploited in the wild.
- How severe is CVE-2026-107297?
- Medium severity, with a CVSS score of 5.9, published 8 October 2026.
- Which products and versions are affected?
- Mcollina Msgpack5 < 6.1.0; msgpack5 (npm) < 6.1.0, SEMVER:introduced=0,fixed=6.1.0.
- Is there a fix for CVE-2026-107297?
- Yes. msgpack5 (npm): upgrade to 6.1.0 or later. Until then: Buffer each complete MessagePack value before decoding it, or limit the number of chunks accepted for a single value. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-107297 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-107297?
- Check whether you run Mcollina Msgpack5 or msgpack5 (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- msgpack5 (npm): upgrade to 6.1.0 or later
npm install msgpack5@6.1.0
Buffer each complete MessagePack value before decoding it, or limit the number of chunks accepted for a single value.
Technical details
The streaming decoder exhibits quadratic complexity (CWE-407) when processing incomplete containers because it reparses from the beginning each time a new chunk arrives, rather than preserving state. A remote attacker with network access can split a single valid MessagePack value across many small chunks to trigger worst-case CPU usage and event loop blocking. The vulnerability is fixed in version 6.1.0 by preserving incremental container state.
Affected products
- mcollina msgpack5 < 6.1.0
Identifiers
- CVE-2026-107297
- GHSA-gcx5-hxj7-gpqq
Timeline
- 2026-10-08: disclosed
- 2026-09-26: patched: patch published to npm