Update dependency svgo to v4.0.1 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
svgo (source)	4.0.0 → 4.0.1

GitHub Vulnerability Alerts

CVE-2026-29074

Summary

SVGO accepts XML with custom entities, without guards against entity expansion or recursion. This can result in a small XML file (811 bytes) stalling the application and even crashing the Node.js process with JavaScript heap out of memory.

Details

The upstream XML parser (sax) doesn't interpret custom XML entities by default. We pattern matched custom XML entities from the DOCTYPE, inserting them into parser.ENTITIES, and enabled unparsedEntities. This gives us the desired behavior of supporting SVGs with entities declared in the DOCTYPE.

However, entities can reference other entities, which can enable small SVGs to explode exponentially when we try to parse them.

Proof of Concept

import { optimize } from 'svgo';

/** Presume that this string was obtained in some other way, such as network. */
const original = `
  <?xml version="1.0"?>
  <!DOCTYPE lolz [
  <!ENTITY lol "lol">
  <!ELEMENT lolz (#PCDATA)>
  <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
  <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
  <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
  <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
  <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
  <!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
  <!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
  <!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
  <!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
  ]>
  <lolz>&lol9;</lolz>
`;

optimize(original);

Impact

If SVGO is run on untrusted input (i.e., user uploaded to server-side application), then the untrusted SVG can effectively stall or crash the application with an SVG < 1 KB in size.

It's unlikely to impact users who just use SVGO locally on their own SVGs or in build pipelines.

Patches

SVGO has patched v4.0.1, v3.3.3, and v2.8.1! However, it's strongly recommended to upgrade to v4 regardless, as previous versions are not officially supported anymore.

Workarounds

== 4.0.0

For v4, users do not specifically have to upgrade SVGO, though it is recommended to do so. A package manager can be used to upgrade sax recursively:

For example:

yarn up -R sax

New options were introduced upstream which makes the way SVGO parses SVGs safe by default.

>= 2.1.0, <= 3.3.2

Users of v3 and v2 will have to take manual action. If users can't upgrade, they may be able to work around this as long as the project doesn't require support for custom XML entities, though it's not a simple flag.

Parse the DOCTYPE directly and check for the presence of custom entities. If entities are present, throw/escape before passing them to SVGO.

+ import SAX from 'sax';
  import { optimize } from 'svgo';

- const original =`
+ let original = `
    <?xml version="1.0"?>
    <!DOCTYPE lolz [
    <!ENTITY lol "lol">
    <!ELEMENT lolz (#PCDATA)>
    <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
    <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
    <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
    <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
    <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
    <!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
    <!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
    <!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
    <!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
    ]>
    <lolz>&lol9;</lolz>
  `;

+ const parser = SAX.parser();
+ /** @&#8203;param {string} doctype */
+ parser.ondoctype = (doctype) => {
+   original = original.replace(doctype, '');
+ }
+ parser.write(original);

  optimize(original);

Resources

• Wikipedia: Billion laughs attack

---

Release Notes

svg/svgo (svgo)

v4.0.1

Compare Source

What's Changed

Dependencies

• Sets minimum version of sax (XML parser) to v1.5.0, which improves built-in guards against entity expansion.

Bug Fixes

• removeEmptyContainers, removed leftover <use> elements referencing an empty container that were removed. By @​johnkenny54 in #​2051
• removeUnknownsAndDefaults, don't remove attributes if they're referenced in attribute selectors (CSS). By @​SethFalco in #​2144

Performance

• convertPathData, refactor to reduce redundant equality checks. By @​Lorfdail in #​1764 and #​2135
• removeHiddenElems, compute styles lazily. By @​Lorfdail in #​1764 and #​2135

Other Changes

• Plugins no longer include if they are enabled or disabled by default, as this was written inconsistently. The --show-plugins argument appends the presets a plugin is in to the end of the line. By @​viralcodex in #​2174
• Plugin/preset types to enforce the name start with preset- if it is a preset (collection of plugins). By @​SethFalco in #​2178

Metrics

Before and after of the browser bundle of each respective version:

	v4.0.0	v4.0.1	Delta
svgo.browser.js	780.2 kB	781.5 kB	⬆️ 1.3 kB

---

Configuration

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