GHSA-496g-mmpw-j9x3 is a medium-severity (CVSS 6.5) CWE-862 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
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 GHSA-496g-mmpw-j9x3.
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-496g-mmpw-j9x3 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 377,166 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.
misskey-jsnpmDescription
Summary
After adding private posts (followers, direct) that you do not have permission to view to your favorites or clips, you can export them to view the contents of the private posts.
PoC
- Create an account (X) for testing and an account (Y) for private posts on the same server.
- Send appropriate content from Y using "Follow"
- Send appropriate content to any user using "Nominate" from Y
- Obtain the URLs for the two posts above using Y's account.
- Query the URLs for the two posts using X and add them to your favorites or clips.
- Export your favorites or clips using X.
- Check the exported data.
Note: Verified in v2025.11.1
Impact
This could allow an attacker to view the contents of private posts. If you have pinned private posts, this could be a real problem, as the ID of the private post can be obtained by viewing the user page on the original server.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | misskey-js | ≥ 13.0.0-beta.16&&< 2025.12.0 | 2025.12.0npm install misskey-js@2025.12.0 |
Detection & mitigation playbook
Open-source dependencyDetect
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 GHSA-496g-mmpw-j9x3 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 GHSA-496g-mmpw-j9x3 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-496g-mmpw-j9x3. 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-496g-mmpw-j9x3 in your dependencies?
O3 Security finds GHSA-496g-mmpw-j9x3 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.