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CVE-2026-68749— Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service

Quick assessment

Affected
rrrene html_sanitize_ex
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

WordPress Formidable Forms是WordPress基金会开源的一款表单创建插件。 René Föhring HtmlSanitizeEx 0.3.1版本至1.5.3之前版本存在资源管理错误漏洞，该漏洞源于CSS scrubber中的正则表达式复杂性低效，可能允许未经身份验证的远程攻击者通过长CSS声明耗尽服务器CPU。

CVSS 8.2 · High EPSS 0.80% · P56

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 3

VendorProduct Version RangeStatus
rrrene html_sanitize_ex 0.3.1< 1.4.5 affected
1.5.0-rc.0< 1.5.3 affected
21f90012eb21aa36f4e3701b7547e12faf0f3c8b< * affected
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I. Basic Information for CVE-2026-68749

Vulnerability Information
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Vulnerability Title
Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service
Source: CVE Program / CVE List V5
Vulnerability Description
Inefficient Regular Expression Complexity vulnerability in the CSS scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to exhaust server CPU via a long CSS declaration in sanitized HTML. The declaration regex in HtmlSanitizeEx.Scrubber.CSS.scrub/1 matches the property name with an unbounded greedy [-\w]+ followed by a mandatory :, so a long run of word characters not followed by a colon makes the engine give back one character at a time and retry the colon at every start offset. The work is quadratic in the length of the run, and no length cap is applied to the CSS handed to the scrubber. An 80 KB <style> body costs roughly 2.4 seconds of scheduler time, so a few concurrent requests saturate the BEAM scheduler pool and make the application unresponsive. The impact is CPU exhaustion only. Nothing is read, modified or disclosed. This issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5
Vulnerability Title
René Föhring HtmlSanitizeEx 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
WordPress Formidable Forms是WordPress基金会开源的一款表单创建插件。 René Föhring HtmlSanitizeEx 0.3.1版本至1.5.3之前版本存在资源管理错误漏洞，该漏洞源于CSS scrubber中的正则表达式复杂性低效，可能允许未经身份验证的远程攻击者通过长CSS声明耗尽服务器CPU。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
rrrene html_sanitize_ex 0.3.1 ~ 1.4.5 cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*
rrrene html_sanitize_ex 21f90012eb21aa36f4e3701b7547e12faf0f3c8b ~ * cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-68749

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 7553 chars
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III. Intelligence Information for CVE-2026-68749

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Patches & Fixes for CVE-2026-68749 (2)

Vendor Advisories for CVE-2026-68749 (2)

News Coverage for CVE-2026-68749 (1)

Same Patch Batch · rrrene · 2026-08-06 · 6 CVEs total

CVE-2026-68750 8.2 HIGH Quadratic sibling re-flattening in the html_sanitize_ex traversal engine allows CPU-exhaus
CVE-2026-66370 4.8 MEDIUM html_sanitize_ex HTML5 scrubber keeps attacker-supplied form-association attributes, allow
CVE-2026-66829 2.3 LOW html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cros
CVE-2026-66843 2.3 LOW html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untr
CVE-2026-68747 2.3 LOW CSS sanitizer allowlist bypass in html_sanitize_ex via non-declaration input

IV. Related Vulnerabilities

Same product: html_sanitize_ex
Same vendor: rrrene
Same weakness: CWE-1333

V. Comments for CVE-2026-68749

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