CSS sanitizer allowlist bypass in html_sanitize_ex via non-declaration input
Summary
| CVE | CVE-2026-68747 |
|---|---|
| State | PUBLISHED |
| Assigner | EEF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-06 16:16:51 UTC |
| Updated | 2026-08-06 22:18:24 UTC |
| 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 1.5.4. |
Risk And Classification
Primary CVSS: v4.0 2.3 LOW from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
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/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
Problem Types: CWE-74 | CWE-74 CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | Secondary | 2.3 | LOW | 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/E:X/C... |
| 4.0 | CNA | CVSS | 2.3 | LOW | 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 |
CVSS v4.0 Breakdown
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/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
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Rrrene | Html Sanitize Ex | affected 0.3.1 1.5.4 semver | Not specified |
| CNA | Rrrene | Html Sanitize Ex | affected 21f90012eb21aa36f4e3701b7547e12faf0f3c8b 0b9f9ad63a7529d4f2c3c1134c371adc3e654308 git | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| osv.dev/vulnerability/EEF-CVE-2026-68747 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | osv.dev | |
| cna.erlef.org/cves/CVE-2026-68747.html | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | cna.erlef.org | |
| github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-87v2-pfhj-r5x7 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| github.com/rrrene/html_sanitize_ex/commit/0b9f9ad63a7529d4f2c3c1134c371a... | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Peter Ullrich (en)
CNA: Jonatan Männchen / EEF (en)
CNA: René Föhring (en)
Additional Advisory Data
Workarounds
CNA: Sanitize with basic_html/1, markdown_html/1 or strip_tags/1, none of which allow <style> elements, or define a custom scrubber that omits it. A Content-Security-Policy style-src directive that permits no external stylesheet origins stops an injected @import from loading, though injected inline rules still apply.