CVE-2026-107297 msgpack5: Quadratic parsing in the streaming decoder
A remote attacker can cause excessive CPU usage and block the event loop by sending fragmented MessagePack data to the streaming decoder.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-107297?
CVE-2026-107297 is a medium-severity denial of service vulnerability in mcollina msgpack5, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-407
Which versions are affected by CVE-2026-107297?
2 open source packages ship an affected version, including msgpack5.
| Package | Affected | Fixed in |
|---|---|---|
msgpack5 npm | All versions | 6.1.0 |
msgpack5 npm | All versions | 6.1.0 |
How do I fix CVE-2026-107297?
Upgrade msgpack5 to 6.1.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-107297 being exploited?
There is no known exploitation of CVE-2026-107297 in the wild and no public exploit code.
Sources
Also known as AZL-106842, GHSA-gcx5-hxj7-gpqq.