How severe is GHSA-3949-f494-cm99?

GHSA-3949-f494-cm99 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-3949-f494-cm99?

GHSA-3949-f494-cm99 affects the following packages: prismjs (npm). Ecosystems affected: npm.

How do I fix GHSA-3949-f494-cm99?

Update prismjs to 1.27.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3949-f494-cm99 is resolved across your whole dependency graph.

How do I detect GHSA-3949-f494-cm99 in my npm dependencies?

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

How do I mitigate GHSA-3949-f494-cm99 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 GHSA-3949-f494-cm99 actively exploited in the wild?

No public exploit code has been indexed for GHSA-3949-f494-cm99 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-3949-f494-cm99?

GHSA-3949-f494-cm99 has an EPSS (Exploit Prediction Scoring System) score of 1.5%, placing it in the 73th 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 GHSA-3949-f494-cm99?

GHSA-3949-f494-cm99 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 GHSA-3949-f494-cm99 published, and has it been updated?

GHSA-3949-f494-cm99 was published on February 22, 2022 and was last updated on November 8, 2023. 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

HIGH severity

Cross-site Scripting in PrismGHSA-3949-f494-cm99

HIGHFix: PrismJS/prism#3341

GHSA-3949-f494-cm99 is a high-severity (CVSS 7.5) Cross-site Scripting (XSS) vulnerability in prismjs. A fix is available for prismjs — see the affected versions and patch details below.

Also known asCVE-2022-23647

Published

Feb 22, 2022

Updated

Nov 8, 2023

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

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 GHSA-3949-f494-cm99.

EPSS Exploitation Probability

via FIRST.org ↗

1.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk

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

How urgent is this, really

GHSA-3949-f494-cm99 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 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.

5Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

prismjsnpm

39.3Mdownloads / week

Description

Impact

Prism's Command line plugin can be used by attackers to achieve an XSS attack. The Command line plugin did not properly escape its output, leading to the input text being inserted into the DOM as HTML code.

Server-side usage of Prism is not impacted. Websites that do not use the Command Line plugin are also not impacted.

Patches

This bug has been fixed in v1.27.0.

Workarounds

Do not use the Command line plugin on untrusted inputs, or sanitized all code blocks (remove all HTML code text) from all code blocks that use the Command line plugin.

References

https://github.com/PrismJS/prism/pull/3341

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`prismjs`	≥ 1.14.0&&< 1.27.0	1.27.0`npm install prismjs@1.27.0`

Affected Products

1 product · 1 configurations

Application

prismprismjs

≥ 1.14.0 && < 1.27.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for prismjs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update prismjs to 1.27.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3949-f494-cm99 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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This issue affects Prism as shipped with all versions of Red Hat Ceph Storage, Red Hat Migration Toolkit for Virtualization, Red Hat OpenShift Container Platform, Red Hat OpenShift Service Mesh, Red Hat Advanced Cluster Security, and Red Hat Gluster Storage. However, this flaw is not known to be exploitable under any…

Product	Fixed in	Advisory
Red Hat Data Grid 8.4.0	`prismjs`	RHSA-2022:8524
RHINT Service Registry 2.3.0 GA	`prismjs`	RHSA-2022:6835

Frequently Asked Questions

### Impact Prism's [Command line plugin](https://prismjs.com/plugins/command-line/) can be used by attackers to achieve an XSS attack. The Command line plugin did not properly escape its output, leading to the input text being inserted into the DOM as HTML code. Server-side usage of Prism is not impacted. Websites that do not use the Command Line plugin are also not impacted. ### Patches This bug has been fixed in v1.27.0. ### Workarounds Do not use the Command line plugin on untrusted inputs, or sanitized all code blocks (remove all HTML code text) from all code blocks that use the Command