---
id: CVE-2026-26028
title: CryptPad is an end-to-end encrypted collaborative office suite
summary: >-
  CryptPad is an end-to-end encrypted collaborative office suite. In versions
  prior to 2026.2.0, the HTML sanitizer in Diffmarked.js can be bypassed due to
  incomplete attribute filtering on restricted tags. The sanitizer validates
  only the…
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
  - CWE-116
published: '2026-05-20'
updated: '2026-07-23'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-26028'
references:
  - url: 'https://github.com/cryptpad/cryptpad/releases/tag/2026.2.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/cryptpad/cryptpad/security/advisories/GHSA-g2g4-47gv-p72v
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.00285
epssPercentile: 0.18692
ingestedAt: '2026-07-23T12:17:55.782Z'
---

## Overview

CryptPad is an end-to-end encrypted collaborative office suite. In versions prior to 2026.2.0, the HTML sanitizer in Diffmarked.js can be bypassed due to incomplete attribute filtering on restricted tags. The sanitizer validates only the src attribute of <iframe>, <video>, and <audio> elements, leaving all other attributes unchecked. As a result, an attacker can inject arbitrary HTML through srcdoc, completely defeating CryptPad's intended bounce sandboxing and enabling link injection or other interactive content within user-controlled documents. The root cause lies in how the sanitizer classifies and enforces tag restrictions: although it defines both forbidden and restricted tag lists, <iframe> is treated as "restricted" rather than "forbidden." Enforcement then inspects only the src attribute, so pairing a benign blob: src with a malicious srcdoc results in unrestricted rendering. This issue has been fixed in version 2026.2.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.