How severe is CVE-2026-107298?

CVE-2026-107298 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-107298?

CVE-2026-107298 affects the following packages: msgpack5 (npm). Ecosystems affected: npm.

How do I fix CVE-2026-107298?

Update msgpack5 to 6.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-107298 is resolved across your whole dependency graph.

How do I detect CVE-2026-107298 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for msgpack5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-107298 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-107298 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-107298 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-107298?

CVE-2026-107298 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 30th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-107298?

CVE-2026-107298 is classified as CWE-674 (CWE-674). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-107298 published, and has it been updated?

CVE-2026-107298 was published on October 8, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

CVE-2026-107298 — msgpack5

MEDIUMFix: mcollina/msgpack5@1e2b587

CVE-2026-107298 is a medium-severity (CVSS 5.3) CWE-674 vulnerability in msgpack5. A fix is available for msgpack5 — see the affected versions and patch details below.

msgpack5: Deeply nested input can exhaust the decoder stack

Also known asGHSA-24ch-f2g6-9hhh

Published

Oct 8, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-107298.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs30th percentile — riskier than 30% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-107298 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

📦msgpack5

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`msgpack5`	all versions	6.1.0`npm install msgpack5@6.1.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for msgpack5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update msgpack5 to 6.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-107298 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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.