# CVE-2026-7808 — EmilStenstrom justhtml

> As of 2026-08-23, CVE-2026-7808 is a CRITICAL-severity vulnerability in EmilStenstrom justhtml, CVSS v3.1 9.8, EPSS 0.3% (27.8th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-7808 as of 2026-08-23; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-08-23

## What is CVE-2026-7808?

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.

The record classifies CVE-2026-7808 under weakness class [CWE-20](https://intel.threadlinqs.com/cwe/CWE-20). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 43 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 9.8 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **CVSS v4.0 base score:** 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 27.8% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 6/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-23

## Is CVE-2026-7808 being exploited?

It currently carries a trending score of 37 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [EmilStenstrom](https://intel.threadlinqs.com/vendors/emilstenstrom): justhtml

## How to fix CVE-2026-7808

No vendor patch reference has been recorded for CVE-2026-7808 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-7808

No threat campaign in the Threadlinqs corpus currently references CVE-2026-7808, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-08-24. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com — vendor advisory](https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-4p64-v8f5-r2gx)

**Third-party advisory**

- [vulncheck.com — third party advisory](https://www.vulncheck.com/advisories/justhtml-before-multiple-security-issues-via-sanitization)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-7808
Full detection coverage and IOCs for threats exploiting CVE-2026-7808 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp