CVE-2025-47935 is a high-severity (CVSS 7.5) CWE-401 vulnerability in multer. A fix is available for multer — see the affected versions and patch details below.
Multer vulnerable to Denial of Service via memory leaks from unclosed streams
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-2025-47935.
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
CVE-2025-47935 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 379,145 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.
multernpmDescription
Multer is a node.js middleware for handling multipart/form-data. Versions prior to 2.0.0 are vulnerable to a resource exhaustion and memory leak issue due to improper stream handling. When the HTTP request stream emits an error, the internal busboy stream is not closed, violating Node.js stream safety guidance. This leads to unclosed streams accumulating over time, consuming memory and file descriptors. Under sustained or repeated failure conditions, this can result in denial of service, requiring manual server restarts to recover. All users of Multer handling file uploads are potentially impacted. Users should upgrade to 2.0.0 to receive a patch. No known workarounds are available.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | multer | all versions | 2.0.0npm install multer@2.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for multer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update multer to 2.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-47935 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-2025-47935 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-47935. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-47935 in your dependencies?
O3 Security finds CVE-2025-47935 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.