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Moderate severityNVD Advisory· Published Mar 3, 2021· Updated Apr 16, 2025

Remote code execution in pug

CVE-2021-21353

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 packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
pugnpm
< 3.0.13.0.1
pug-code-gennpm
< 2.0.32.0.3
pug-code-gennpm
>= 3.0.0, < 3.0.23.0.2

Affected products

1

Patches

1
991e78f7c422

fix: sanitise and escape the `pretty` option (#3314)

https://github.com/pugjs/pugForbes LindesayFeb 28, 2021via ghsa
commit
1 file changed · +11 −2
  • packages/pug-code-gen/index.js+11 −2 modified
    @@ -57,6 +57,11 @@ function Compiler(node, options) {
   if (this.pp && typeof this.pp !== 'string') {
     this.pp = '  ';
   }
+  if (this.pp && !/^\s+$/.test(this.pp)) {
+    throw new Error(
+      'The pretty parameter should either be a boolean or whitespace only string'
+    );
+  }
   this.debug = false !== options.compileDebug;
   this.indents = 0;
   this.parentIndents = 0;
@@ -452,7 +457,9 @@ Compiler.prototype = {
   visitMixinBlock: function(block) {
     if (this.pp)
       this.buf.push(
-        "pug_indent.push('" + Array(this.indents + 1).join(this.pp) + "');"
+        'pug_indent.push(' +
+          stringify(Array(this.indents + 1).join(this.pp)) +
+          ');'
       );
     this.buf.push('block && block();');
     if (this.pp) this.buf.push('pug_indent.pop();');
@@ -504,7 +511,9 @@ Compiler.prototype = {
       this.mixins[key].used = true;
       if (pp)
         this.buf.push(
-          "pug_indent.push('" + Array(this.indents + 1).join(pp) + "');"
+          'pug_indent.push(' +
+            stringify(Array(this.indents + 1).join(pp)) +
+            ');'
         );
       if (block || attrs.length || attrsBlocks.length) {
         this.buf.push(name + '.call({');

Vulnerability mechanics

Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

9

News mentions

0

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