CVE-2026-44646

Context.spawn() in liquidjs creates a child Context for the {% render %} tag but does not propagate the parent context's resolved ownPropertyOnly value. The new context re-derives ownPropertyOnly from opts.ownPropertyOnly (the instance-level option), silently discarding any RenderOptions.ownPropertyOnly override that was supplied to parseAndRender(). As a result, a developer who runs a Liquid instance with the backwards-compatible ownPropertyOnly:false and then locks down an untrusted render with parseAndRender(..., { ownPropertyOnly: true }) still leaks prototype-chain properties from inside any {% render %} partial. This is a distinct exploit surface from the previously identified array-filter variants (where, reject, group_by, find, find_index, has), the underlying root cause in Context.spawn() is shared, but {% render %} is a separately reachable sink that needs no filter usage.

Details

The bug is in Context.spawn():

// src/context/context.ts:105-114
public spawn (scope = {}) {
  return new Context(scope, this.opts, {
    sync: this.sync,
    globals: this.globals,
    strictVariables: this.strictVariables
    // <-- ownPropertyOnly is missing here
  }, {
    renderLimit: this.renderLimit,
    memoryLimit: this.memoryLimit
  })
}

The constructor resolves ownPropertyOnly as:

// src/context/context.ts:47
this.ownPropertyOnly = renderOptions.ownPropertyOnly ?? opts.ownPropertyOnly

Because spawn() passes a RenderOptions object with no ownPropertyOnly, the child context falls back to opts.ownPropertyOnly (the instance-level option), throwing away any per-render override that the parent context had applied. this.opts is the raw normalized instance options object; it is not mutated to reflect render-time overrides.

The {% render %} tag at src/tags/render.ts:51-77 calls spawn() to build the partial's isolated scope:

* render (ctx: Context, emitter: Emitter): Generator<unknown, void, unknown> {
  const { liquid, hash } = this
  const filepath = (yield renderFilePath(this['file'], ctx, liquid)) as string
  assert(filepath, () => `illegal file path "${filepath}"`)

  const childCtx = ctx.spawn()                    // <-- ownPropertyOnly lost here
  const scope = childCtx.bottom()
  __assign(scope, yield hash.render(ctx))
  ...
  const templates = (yield liquid._parsePartialFile(filepath, childCtx.sync, this['currentFile'])) as Template[]
  yield liquid.renderer.renderTemplates(templates, childCtx, emitter)
}

All template variable lookups inside the partial then go through childCtx.readProperty() (src/context/context.ts:123-135), which calls readJSProperty(obj, key, this.ownPropertyOnly). With childCtx.ownPropertyOnly === false (inherited from opts), the protective check at src/context/context.ts:138-141 is skipped and prototype-chain properties are returned to the template:

export function readJSProperty (obj: Scope, key: PropertyKey, ownPropertyOnly: boolean) {
  if (ownPropertyOnly && !hasOwnProperty.call(obj, key) && !(obj instanceof Drop)) return undefined
  return obj[key]
}

The {% include %} tag is not affected: it does not call spawn(); it pushes onto the parent context's scope stack (src/tags/include.ts:40), so the parent's resolved ownPropertyOnly continues to apply.

Trust model / why this matters: RenderOptions.ownPropertyOnly is documented (src/liquid-options.ts:108-111) as "Same as ownPropertyOnly on LiquidOptions, but only for current render() call". It exists precisely so that developers running a non-strict instance can lock down individual untrusted renders. That contract is broken, the override is silently dropped at every partial boundary.

PoC

mkdir -p /tmp/render-poc
printf '{{ user.passwordHash }}' > /tmp/render-poc/_user.liquid

node -e "
const { Liquid } = require('./dist/liquid.node.js');
const liquid = new Liquid({ ownPropertyOnly: false, root: '/tmp/render-poc' });

class User { constructor(n){ this.name = n; } }
User.prototype.passwordHash = 'bcrypt\$secret';
const u = new User('alice');

liquid.parseAndRender(
  'Direct:[{{ user.passwordHash }}] Render:[{% render \"_user.liquid\", user: user %}]',
  { user: u },
  { ownPropertyOnly: true }
).then(console.log);
"

Verified output on liquidjs 10.25.7:

Direct:[] Render:[bcrypt$secret]

The top-level expression {{ user.passwordHash }} is correctly blocked by the per-render ownPropertyOnly:true, but the same expression inside the partial loaded by {% render %} returns the prototype-chain property, proof that Context.spawn() discarded the override.

• Information disclosure: Any prototype-chain property of objects passed into a {% render %} partial, including secrets, hashes, internal state, framework-injected helpers, becomes readable from inside the partial template, even when the developer used the documented per-render lockdown.
• Realistic threat model: Applications that maintain ownPropertyOnly:false for backwards compatibility (or because their data layer relies on prototype methods) and lock down untrusted-template renders with parseAndRender(..., { ownPropertyOnly:true }) are protected at the top level but silently exposed inside any partial. User-controllable template content (CMS snippets, theme partials, email templates) that uses {% render %} becomes an info-leak primitive.
• Distinct from existing CVE-2022-25948: the prior advisory only covered direct use of ownPropertyOnly:false; this is a failure of the documented mitigation (ownPropertyOnly:true per-render override), not a missing setting.
• Distinct from the array-filter variant: same spawn() root cause, but exploitable without invoking where/reject/group_by/find/find_index/has, only requires that the template uses {% render %} (a basic templating feature) and that one of the rendered values has prototype-chain properties.

CVE-2026-44646 has a CVSS score of 5.3 (Medium). 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

Propagate ownPropertyOnly (and any other security-relevant render options) inside Context.spawn():

// src/context/context.ts
public spawn (scope = {}) {
  return new Context(scope, this.opts, {
    sync: this.sync,
    globals: this.globals,
    strictVariables: this.strictVariables,
    ownPropertyOnly: this.ownPropertyOnly   // <-- propagate resolved per-render value
  }, {
    renderLimit: this.renderLimit,
    memoryLimit: this.memoryLimit
  })
}

Passing this.ownPropertyOnly (the resolved value, not this.opts.ownPropertyOnly) ensures any RenderOptions.ownPropertyOnly override flows into spawned child contexts. This single change closes both the {% render %} pathway documented here and the array-filter pathway tracked separately. A regression test should assert that a partial rendered via {% render %} honours parseAndRender(..., { ownPropertyOnly: true }) against an object with prototype-chain properties.

1. What is CVE-2026-44646? CVE-2026-44646 is a medium-severity security vulnerability in liquidjs (npm), affecting versions <= 10.25.7. No fixed version is listed yet.
2. How severe is CVE-2026-44646? CVE-2026-44646 has a CVSS score of 5.3 (Medium). 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-2026-44646? liquidjs (npm) versions <= 10.25.7 is affected.
4. Is there a fix for CVE-2026-44646? No fixed version is listed for CVE-2026-44646 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-44646 exploitable, and should I be worried? Whether CVE-2026-44646 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-2026-44646 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.