msgpack5: Deeply nested input can exhaust the decoder stack

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-107298: 0.37% estimated exploitation activity in the next 30 days; percentile 31.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The decoder has no nesting-depth limit for arrays and maps. An attacker who can provide MessagePack input can use deeply nested containers to exhaust the JavaScript call stack and interrupt the process or request handler. Patches The decoder now limits nesting depth to 100 by default and throws Maximum decode depth exceeded. Applications can configure the limit with the maxDepth option. Workarounds Reject deeply nested input before decoding, isolate decoding in a worker, or enforce a trusted schema with a bounded nesting depth.

Published by the source

8 Oct 2026, 17:39 UTC

Last modified by the source

8 Oct 2026, 18:00 UTC

Source last checked

26 Oct 2026, 13:07 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-24ch-f2g6-9hhh

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-24ch-f2g6-9hhh

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-24ch-f2g6-9hhh

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# Patch Next advisory brief: CVE-2026-107298

Advisory: msgpack5: Deeply nested input can exhaust the decoder stack
IDs: CVE-2026-107298, GHSA-24ch-f2g6-9hhh
Record: https://patchnext.com/advisories/cve-2026-107298 (revision 3, source checked 26 Oct 2026, 13:07 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: msgpack5 6.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm msgpack5: affected < 6.1.0; fixed in 6.1.0

## Suggested inspection (read-only)
- `npm ls msgpack5 --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on msgpack5.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-24ch-f2g6-9hhh (GitHub-reviewed advisory GHSA-24ch-f2g6-9hhh lists affected ranges: npm msgpack5 >=0 <6.1.0)
- Verified: https://osv.dev/vulnerability/GHSA-24ch-f2g6-9hhh (OSV record GHSA-24ch-f2g6-9hhh lists affected ranges: npm msgpack5 >=0 <6.1.0 (fixed))

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