Is CVE-2026-8630 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-8630 being exploited in the wild.

How severe is CVE-2026-8630?

Medium severity, with a CVSS score of 6.1, published 23 August 2026.

Which products and versions are affected?

justhtml (PyPI) ECOSYSTEM:introduced=0,fixed=1.12.0.

Is there a fix for CVE-2026-8630?

Yes. justhtml (PyPI): upgrade to 1.12.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-8630 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-8630?

Check whether you run justhtml (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-8630: justhtml mutation XSS in raw-text element serialization

CVE-2026-8630 · Severity: medium · CVSS 6.1 · Published 2026-08-23

justhtml is a library used to sanitize and process HTML content programmatically. The library contains a vulnerability in how it serializes HTML when custom sanitization policies allow raw-text elements like style and script tags. An attacker can craft malicious text content within these elements that breaks out of the raw-text context and injects arbitrary HTML, potentially leading to script execution in applications that use non-default sanitization policies.

Technologies: justhtml (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-8630 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-8630 being exploited in the wild.
How severe is CVE-2026-8630?: Medium severity, with a CVSS score of 6.1, published 23 August 2026.
Which products and versions are affected?: justhtml (PyPI) ECOSYSTEM:introduced=0,fixed=1.12.0.
Is there a fix for CVE-2026-8630?: Yes. justhtml (PyPI): upgrade to 1.12.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-8630 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-8630?: Check whether you run justhtml (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

justhtml (PyPI): upgrade to 1.12.0 or later
```
pip install "justhtml>=1.12.0"
```

Technical details

This is a mutation XSS (mXSS) vulnerability in the serialize.py module's handling of raw-text elements. The root cause is that text nodes within style and script elements are serialized verbatim without HTML escaping via the _serialize_text_for_parent() function. When a DOM tree is processed through sanitize_dom() with a custom policy that preserves these elements, an attacker can inject text containing a matching closing tag sequence (e.g., "</style>" within a style element) to break out of the raw-text context and inject arbitrary HTML. The attack requires either programmatic DOM construction with attacker input or a custom sanitization policy that retains script/style elements; the default policy is not affected. Patched in version 1.12.0.

Affected products

justhtml justhtml <= 1.11.0

Identifiers

CVE-2026-8630
GHSA-qvc2-mg72-jjhx

Timeline

2026-03-18: disclosed
2026-03-18: patched: Version 1.12.0 released

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.