GHSA-mj3g-7xcc-x4vh is a high-severity (CVSS 7.3) CWE-1321 vulnerability in @phun-ky/defaults-deep. O3 Security confirms whether GHSA-mj3g-7xcc-x4vh is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
@phun-ky/defaults-deep Has a Prototype Pollution issue via Unsafe Recursive Property Merging
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 GHSA-mj3g-7xcc-x4vh.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-mj3g-7xcc-x4vh plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 373,366 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@phun-ky/defaults-deepnpmDescription
Impact
A prototype pollution vulnerability exists in @phun-ky/defaults-deep prior to version 2.0.5.
The library recursively merged user-supplied objects without filtering unsafe property names such as __proto__, constructor, and prototype. An attacker able to supply crafted input could cause properties to be written to Object.prototype, resulting in prototype pollution affecting all objects within the running process.
Applications that pass untrusted input to defaultsDeep() may be impacted. Depending on how the application uses merged objects, this could lead to unexpected behavior, logic bypasses, denial of service, or other security issues.
Patches
This issue has been fixed in version 2.0.5.
Users should upgrade to version 2.0.5 or later.
The fix prevents unsafe prototype-related keys (__proto__, constructor, and prototype) from being processed during recursive merge operations and includes regression tests covering known prototype pollution vectors.
Workarounds
Users unable to upgrade should ensure that untrusted input is sanitized before being passed to defaultsDeep().
At a minimum, applications should reject or remove the following property names from all levels of user-controlled objects:
__proto__constructorprototype
Upgrading to a patched version remains the recommended mitigation.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @phun-ky/defaults-deep | all versions | 2.0.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @phun-ky/defaults-deep. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @phun-ky/defaults-deep to 2.0.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mj3g-7xcc-x4vh 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.
How O3 protects you
O3 pinpoints whether GHSA-mj3g-7xcc-x4vh is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-mj3g-7xcc-x4vh. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mj3g-7xcc-x4vh in your dependencies?
O3 detects GHSA-mj3g-7xcc-x4vh across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.