What is CVE-2021-3801?

CVE-2021-3801 is a medium-severity vulnerability in Prismjs Prism, classified under Inefficient Regular Expression Complexity. CVSS score: 6.5/10. Published 2021-09-15.

How severe is CVE-2021-3801?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Prismjs Prism

CVE-2021-3801

prism is vulnerable to Inefficient Regular Expression Complexity

Vulnerability class: ReDoS (Regular Expression Denial of Service)

Published 2021-09-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.010 (63.6th percentile), scored 2026-10-23.

Low probability of exploitation in the next 30 days, but still tracked. 64th percentile — 63.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: -0.000

Affected products

Prismjs Prism
Prismjs Prismjs/prism — versions unspecified

Weakness classification (CWE)

CWE-1333 — Inefficient Regular Expression Complexity

References

huntr.dev/bounties/8c16ab31-6eb6-46d1-b9a4-387222fe1b8a (Exploit, Patch, Third Party Advisory, Issue Tracking)
github.com/prismjs/prism/commit/0ff371bb4775a131634f47d0fe85794c547232f9 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3801?: CVE-2021-3801 is a medium-severity vulnerability in Prismjs Prism, classified under Inefficient Regular Expression Complexity. CVSS score: 6.5/10. Published 2021-09-15.
How severe is CVE-2021-3801?: Medium severity. CVSS v3 base score is 6.5 out of 10.