EmilStenstrom justhtml up to 1.15.x HTML Sanitization sanitize/sanitize_dom HTML injection

Summaryinfo

A vulnerability has been found in EmilStenstrom justhtml up to 1.15.x and classified as problematic. This vulnerability affects the function sanitize/sanitize_dom of the component HTML Sanitization. Performing a manipulation results in HTML injection. This vulnerability is identified as CVE-2026-7808. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic has been found in EmilStenstrom justhtml up to 1.15.x. This affects the function sanitize/sanitize_dom of the component HTML Sanitization. The manipulation with an unknown input leads to a html injection vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. The summary by CVE is:

justhtml before 1.16.0 contains multiple HTML sanitization bypass issues that can allow active/dangerous content (e.g., script or style) to survive sanitization, potentially leading to cross-site scripting. The issues primarily affect advanced usage rather than the default JustHTML(..., sanitize=True) path for ordinary parsed HTML: mutating or reusing sanitization policy objects (including exported defaults) could weaken later sanitization; programmatic DOM input to sanitize()/sanitize_dom() could miss mixed-case tag names (e.g., ScRiPt, StYlE); crafted programmatic doctype names could serialize into active markup; and custom policies preserving SVG or MathML could allow animation elements, presentation attributes with external url(...) references, or DOM trees mislabeled as namespace="html" to bypass foreign-content checks. Fixed in 1.16.0.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-7808 since 05/04/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 1.16.0 eliminates this vulnerability.

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Productinfo

Vendor

• EmilStenstrom

Name

• justhtml

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15

Website

• Product: https://github.com/EmilStenstrom/justhtml/

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