Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The msgpack5 npm package is vulnerable in versions before 6.1.0, and the fix is in 6.1.0. The streaming decoder recurses once for each complete value in a chunk, so a single chunk holding many small valid MessagePack values can exhaust the JavaScript call stack and interrupt the process or stream. The source does not say what access an attacker needs beyond being able to send data to the decoder. Upgrade to msgpack5 6.1.0 or later; the source's workaround is to limit the number of values accepted in one chunk or split large batches before decoding.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 7.5 | High | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0043, the 37th percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 13:33 UTC First seen by agentprime
- 31 Oct 2026, 13:33 UTC Confirmed by OSV