How severe is CVE-2025-66402?

No CVSS score has been assigned to CVE-2025-66402 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-66402?

CVE-2025-66402 affects the following packages: misskey-js (npm). Ecosystems affected: npm.

How do I fix CVE-2025-66402?

Update misskey-js to 2025.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66402 is resolved across your whole dependency graph.

How do I detect CVE-2025-66402 in my npm dependencies?

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

How do I mitigate CVE-2025-66402 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.

How does O3 Security protect against CVE-2025-66402?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-66402 can be triaged on real exposure rather than presence alone.

Is CVE-2025-66402 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-66402 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-2025-66402?

CVE-2025-66402 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 25th 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.

When was CVE-2025-66402 published, and has it been updated?

CVE-2025-66402 was published on December 15, 2025 and was last updated on August 12, 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

CVE-2025-66402 — misskey-js

Fix: misskey-dev/misskey@dc77d59

CVE-2025-66402 is a security vulnerability in misskey-js. A fix is available for misskey-js — see the affected versions and patch details below.

misskey.js's export data contains private post data

Also known asGHSA-496g-mmpw-j9x3

Published

Dec 15, 2025

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 19, 2026 · OSV.dev, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66402.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs25th percentile — riskier than 25% of all scored CVEsHighest risk

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.

Real-World Exposure

1 pkg affected

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.

1other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

misskey-jsnpm

2Kdownloads / week

Description

Misskey is an open source, federated social media platform. Starting in version 13.0.0-beta.16 and prior to version 2025.12.0, an actor who does not have permission to view favorites or clips can can export the posts and view the contents. Version 2025.12.0 fixes the issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`misskey-js`	≥ 13.0.0-beta.16&&< 2025.12.0	2025.12.0`npm install misskey-js@2025.12.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for misskey-js, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update misskey-js to 2025.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66402 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-66402 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2025-66402. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2025-66402 in your dependencies?

O3 Security finds CVE-2025-66402 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works