CVE-2021-21353: Remote code execution in pug

Severity: critical (CVSS 9.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 4.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-03-03 · updated 2026-06-17
Weakness: CWE-74

Description

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.

Affected products

pugjs pug: before 3.0.1 — fixed in 3.0.1
pugjs Pug-Code-Gen: before 2.0.3; from 3.0.0 before 3.0.2 — fixed in 2.0.3, 3.0.2

How to fix

Upgrade to a fixed version: pugjs pug 3.0.1; pugjs Pug-Code-Gen 2.0.3, 3.0.2. Check the vendor advisory for mitigations.

References

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