How severe is CVE-2021-42648?

CVE-2021-42648 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-42648?

CVE-2021-42648 affects the following packages: code-server (npm). Ecosystems affected: npm.

How do I fix CVE-2021-42648?

Update code-server to 3.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-42648 is resolved across your whole dependency graph.

How do I detect CVE-2021-42648 in my npm dependencies?

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

How do I mitigate CVE-2021-42648 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-42648 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-42648, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-42648?

CVE-2021-42648 has an EPSS (Exploit Prediction Scoring System) score of 0.9%, placing it in the 59th 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.

What type of vulnerability is CVE-2021-42648?

CVE-2021-42648 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-42648 published, and has it been updated?

CVE-2021-42648 was published on May 11, 2022 and was last updated on October 20, 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

MEDIUM severity

CVE-2021-42648 — code-server

MEDIUMFix: coder/code-server#4430

CVE-2021-42648 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in code-server. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for code-server — see the affected versions and patch details below.

Cross site scripting in code-server

Also known asGHSA-2gp3-6c9p-jp7w

Published

May 11, 2022

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Nov 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.9%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs59th percentile — riskier than 59% of all scored CVEsHighest risk

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

How urgent is this, really

Where this sits among everything scored

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.

2other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

code-servernpm

8Kdownloads / week

Description

Cross-site scripting (XSS) vulnerability exists in Coder Code-Server before 3.12.0, allows attackers to execute arbitrary code via crafted URL.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`code-server`	all versions	3.12.0`npm install code-server@3.12.0`

Affected Products

1 product · 1 configurations

Application

code-servercoder

< 3.12.0

range

Exploits & PoCs

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

Cross-site scripting (XSS) vulnerability exists in Coder Code-Server bef…

github.comNVDMay 2022

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for code-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update code-server to 3.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-42648 is resolved across your whole dependency graph.
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

Cross-site scripting (XSS) vulnerability exists in Coder Code-Server before 3.12.0, allows attackers to execute arbitrary code via crafted URL.

O3 Security · Impact-Aware SCA

Is CVE-2021-42648 in your dependencies?

Find it across npm, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

6.1/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No Nuclei template or Metasploit module yet. 1 public proof-of-concept reference is listed on this page.

OpenSSF Scorecard

Package health score

code-server

6.6/10

Code-Review10/10

Maintained10/10

Branch-ProtectionN/A

Assessed Oct 26, 2026

Timeline

Disclosed

May 11, 2022

First exploit

May 20, 2022

Last updated

Oct 20, 2026

Identifiers

CVE-2021-42648

GHSA-2gp3-6c9p-jp7w

References

Advisorynvd.nist.gov · CVE 2021 42648 Fixgithub.com Webgithub.com Packagegithub.com · code server

Related vulnerabilities

Also affects code-server

This CVE is medium severity; 3 of 3 other CVEs affecting code-server are rated as high or higher (top: critical).

CVE-2025-47269CVE-2023-26114CVE-2021-3810

Same weakness: CWE-79

This CVE is medium severity; 3 of 5 other CVEs with CWE-79 are rated as high or higher (top: high).

CVE-2026-126075CVE-2026-126063CVE-2026-110802CVE-2026-123364CVE-2026-118670Browse all CWE-79

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 20, 2026