CVE-2019-20041 — wp_kses_bad_protocol in wp-includes/kses

wp_kses_bad_protocol in wp-includes/kses.php in WordPress before 5.3.1 mishandles the HTML5 colon named entity, allowing attackers to bypass input sanitization, as demonstrated by the javascript: substring.

01What is this vulnerability?

wp_kses_bad_protocol in wp-includes/kses.php in WordPress before 5.3.1 mishandles the HTML5 colon named entity, allowing attackers to bypass input sanitization, as demonstrated by the javascript: substring.

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2019-12-27T07:14:52.000Z
• Last modified: 2024-08-05T02:32:10.499Z

09References

• wordpress.org — https://wordpress.org/news/2019/12/wordpress-5-3-1-security-and-maintenance-rele…
• github.com — https://github.com/WordPress/wordpress-develop/commit/b1975463dd995da19bb40d3fa0…
• seclists.org — https://seclists.org/bugtraq/2020/Jan/8
• www.debian.org — https://www.debian.org/security/2020/dsa-4599
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2020/01/msg00010.html
• www.debian.org — https://www.debian.org/security/2020/dsa-4677