What is CVE-2021-21353?

CVE-2021-21353 is a medium-severity vulnerability in Pugjs Pug, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 6.8/10. Published 2021-03-03.

How severe is CVE-2021-21353?

Medium severity. CVSS v3 base score is 6.8 out of 10.

Is CVE-2021-21353 known to be exploited?

3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

RCE in Pugjs Pug

CVE-2021-21353

Pug is an npm package which is a high-performance template engine. In pug before version 3.0.1, if a remote attacker was able to control the `pretty` option of the pug compiler, e.g. if you spread a user provided object such as the query parameters of a request into the pug template inputs, it was possible for them to achieve remote code execution on the node.js backend. This is fixed in version 3.0.1. This advisory applies to multiple pug packages including "pug", "pug-code-gen". pug-code-gen has a backported fix at version 2.0.3. This advisory is not exploitable if there is no way for un-trusted input to be passed to pug as the `pretty` option, e.g. if you compile templates in advance before applying user input to them, you do not need to upgrade.

Published 2021-03-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.043 (90.8th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 91st percentile — 90.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.043 · newest: 0.043 · change: 0.000

Affected products

Pugjs Pug — versions < 3.0.1
Pugjs Pug-Code-Gen

Weakness classification (CWE)

Public proof-of-concept exploits

References

github.com/pugjs/pug/security/advisories/GHSA-p493-635q-r6gr (Third Party Advisory)
github.com/pugjs/pug/issues/3312 (Exploit, Patch, Third Party Advisory)
github.com/pugjs/pug/pull/3314 (Patch, Third Party Advisory)
github.com/pugjs/pug/commit/991e78f7c4220b2f8da042877c6f0ef5a4683be0 (Patch, Third Party Advisory)
github.com/pugjs/pug/releases/tag/pug@3.0.1 (Third Party Advisory, Release Notes)
www.npmjs.com/package/pug (Product, Third Party Advisory)
www.npmjs.com/package/pug-code-gen (Product, Third Party Advisory)

Frequently asked questions

What is CVE-2021-21353?: CVE-2021-21353 is a medium-severity vulnerability in Pugjs Pug, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 6.8/10. Published 2021-03-03.
How severe is CVE-2021-21353?: Medium severity. CVSS v3 base score is 6.8 out of 10.
Is CVE-2021-21353 known to be exploited?: 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.