CVE-2026-4671 PUBLISHED

justhtml before 1.18.0 Denial of Service via CSS Selector

Assigner: VulnCheck
Reserved: 23.03.2026 Published: 23.08.2026 Updated: 23.08.2026

justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification. Applications that evaluate attacker-controlled selector strings (via query(), matches(), or selector-based transforms), run selector matching over very large untrusted documents, construct DOM trees from untrusted structure, or enable linkification over attacker-controlled text may consume disproportionate CPU or memory. Triggers include oversized selectors, large selector lists, oversized compound selectors, long combinator chains, deeply nested functional pseudo-classes, repeated token/positional matching, cyclic DOM graphs causing non-terminating traversal, and punctuation-heavy or trailing-bracket linkification input. These are availability-only concerns and do not by themselves allow script execution, data disclosure, or sanitizer bypass. Default JustHTML(sanitize=True) usage is not expected to be exposed, since selectors are normally supplied by application code.

Metrics

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS Score: 8.7

Product Status

Vendor EmilStenstrom
Product justhtml
Versions Default: unaffected
  • affected from 0 to 1.18.0 (excl.)
  • Version 1.18.0 is unaffected

Credits

  • EmilStenstrom coordinator

References

Problem Types

  • Uncontrolled Resource Consumption CWE