CVE-2026-31938

Workarounds

Sanitize user input before passing it to the output method.

User control of the options argument of the output function allows attackers to inject arbitrary HTML (such as scripts) into the browser context the created PDF is opened in. The affected overloads and options are:

• "pdfobjectnewwindow": the pdfObjectUrl option and the entire options object, which is JSON-serialized and included verbatim in the generated HTML-string.
• "pdfjsnewwindow": the pdfJsUrl and filename options
• "dataurlnewwindow": the filename option

The vulnerability can be exploited in the following scenario: the attacker provides values for the output options, for example via a web interface. These values are then passed unsanitized (automatically or semi-automatically) to the attack victim. The victim creates and opens a PDF with the attack vector using one of the vulnerable method overloads inside their browser. The attacker can thus inject scripts that run in the victims browser context and can extract or modify secrets from this context.

Example attack vector:

import { jsPDF } from 'jspdf';
const doc = new jsPDF();

const payload =  'x\"></iframe><script>window.__n=1</script><iframe src="';

doc.output('pdfjsnewwindow', {
  filename: payload,
  pdfJsUrl: 'viewer.html'
});

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2026-31938 has a CVSS score of 9.6 (Critical). The vector is network-reachable, no privileges required, and user interaction required. 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 (4.2.1); upgrading removes the vulnerable code path.

Kodem intelligence

The vulnerability has been fixed in [email protected].

1. What is CVE-2026-31938? CVE-2026-31938 is a critical-severity cross-site scripting (XSS) vulnerability in jspdf (npm), affecting versions <= 4.2.0. It is fixed in 4.2.1. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2026-31938? CVE-2026-31938 has a CVSS score of 9.6 (Critical). 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 jspdf are affected by CVE-2026-31938? jspdf (npm) versions <= 4.2.0 is affected.
4. Is there a fix for CVE-2026-31938? Yes. CVE-2026-31938 is fixed in 4.2.1. Upgrade to this version or later.
5. Is CVE-2026-31938 exploitable, and should I be worried? Whether CVE-2026-31938 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-2026-31938 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-2026-31938? Upgrade jspdf to 4.2.1 or later.