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MEDIUM severity

CVE-2020-8823 — sockjs

MEDIUM

CVE-2020-8823 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in sockjs. 1 public exploit reference exists, so weaponization risk is real. A fix is available for sockjs — see the affected versions and patch details below.

Cross-site scripting in SocksJS-node

Also known asGHSA-hh8v-jmh3-9437SNYK-JS-SOCKJS-548397
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk
0.26%0.97%1.68%2.39%0.8%1.9%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-8823 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 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.

776other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
sockjsnpm
13.6Mdownloads / week

Description

htmlfile in lib/transport/htmlfile.js in SockJS before 0.3.0 is vulnerable to Reflected XSS via the /htmlfile c (aka callback) parameter.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmsockjsall versions0.3.0npm install sockjs@0.3.0

Affected Products

1 product · 1 configurations
Application
sockjssockjs_project
< 0.3.0
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.

htmlfile in lib/transport/htmlfile.js in SockJS before 0.3.0 is vulnerab…

github.comNVDJan 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 sockjs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update sockjs to 0.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-8823 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

htmlfile in lib/transport/htmlfile.js in SockJS before 0.3.0 is vulnerable to Reflected XSS via the /htmlfile c (aka callback) parameter.
O3 Security · Impact-Aware SCA

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CVE-2020-8823: sockjs XSS — Fixed in 0.3.0