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CVE-2026-26028— CryptPad: Sanitizer Bypass in Diffmarked.js Allows Arbitrary HTML Injection and Potential XSS

Quick assessment

Affected
cryptpad cryptpad
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

CryptPad是CryptPad开源的一个协作办公套件。 CryptPad 2026.2.0之前版本存在跨站脚本漏洞，该漏洞源于HTML清理器对受限标签属性过滤不完整，可能导致攻击者注入任意HTML并绕过沙箱限制。

CVSS 6.1 · Medium EPSS 0.29% · P19

Affected Version Matrix 1

VendorProduct Version RangeStatus
cryptpad cryptpad < 2026.2.0 affected
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I. Basic Information for CVE-2026-26028

Vulnerability Information
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Vulnerability Title
CryptPad: Sanitizer Bypass in Diffmarked.js Allows Arbitrary HTML Injection and Potential XSS
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对输出编码和转义不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
CryptPad 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
CryptPad是CryptPad开源的一个协作办公套件。 CryptPad 2026.2.0之前版本存在跨站脚本漏洞，该漏洞源于HTML清理器对受限标签属性过滤不完整，可能导致攻击者注入任意HTML并绕过沙箱限制。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
cryptpad cryptpad < 2026.2.0 -

II. Public POCs for CVE-2026-26028

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III. Intelligence Information for CVE-2026-26028

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Vendor Advisories for CVE-2026-26028 (1)

Vendor Pages for CVE-2026-26028 (1)

IV. Related Vulnerabilities

Same product: cryptpad
Same vendor: cryptpad
Same weakness: CWE-116

V. Comments for CVE-2026-26028

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