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Not in CISA KEV
HIGH severity

CVE-2020-36048 — engine.io

HIGHFix: socketio/engine.io@734f9d1

CVE-2020-36048 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in engine.io. 1 public exploit reference exists, so weaponization risk is real. A fix is available for engine.io — see the affected versions and patch details below.

Resource exhaustion in engine.io

Also known asGHSA-j4f2-536g-r55m
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
3.3%probability of exploitation in next 30 days
Lower Risk+0.04%
Lower risk than most CVEs88th percentile — riskier than 88% of all scored CVEsHighest risk
0.00%1.39%2.78%4.17%0.5%3.3%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-36048 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 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

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.

258other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
engine.ionpm
19.0Mdownloads / week

Description

Engine.IO before 4.0.0 and 3.6.0 allows attackers to cause a denial of service (resource consumption) via a POST request to the long polling transport.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmengine.ioall versions3.6.0npm install engine.io@3.6.0

Affected Products

1 product · 1 configurations
Application
engine.iosocket
< 4.0.0
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Engine.IO before 4.0.0 allows attackers to cause a denial of service (re…

blog.caller.xyzNVDJan 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update engine.io to 3.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-36048 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

Engine.IO before 4.0.0 and 3.6.0 allows attackers to cause a denial of service (resource consumption) via a POST request to the long polling transport.
O3 Security · Impact-Aware SCA

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CVE-2020-36048: engine.io DoS — Fixed in 3.6.0