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Fencer Intel
medium 6.1

CVE-2026-74793 json

justhtml before 3.11.0 XSS via selectedcontent projection

published 3mo ago modified 30d ago also EUVD-2026-64656 , GHSA-gjf2-f4jc-69xf

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository EmilStenstrom/justhtml. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
6.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

justhtml before 3.11.0 contains a cross-site scripting vulnerability where the default sanitizer bypasses event handler removal in selectedcontent projections. Attackers can inject SVG or MathML elements with event handlers that are cloned and reinserted into output without sanitization, enabling stored or reflected XSS attacks.

Patch / fix

  • EmilStenstrom justhtml 3.11.0

Is CVE-2026-74793 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
2mo ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-gjf2-f4jc-69xf referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CNA 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Inferred packages

No advisory lists a package for this vulnerability yet. The CVE names these as products and links their GitHub repository, and the package registry names the same repository, so they are probably the affected packages. Low confidence: the versions are the CVE’s own for the product, and a stack check reports the package as unchecked when there are none.

ecosystem package repository affected
pypi justhtml emilstenstrom/justhtml no versions given

Affected products

  • EmilStenstrom justhtml

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of EmilStenstrom/justhtml published their own advisory on GitHub. Reviewed sources take precedence over it.