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CVE Record

CVE-2019-20041: wp_kses_bad_protocol in wp-includes/kses.php in WordPress before 5.3.1 mishandles the HTML5 colon named ent...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2019-20041 is a WordPress input-sanitization flaw fixed in WordPress 5.3.1. Older WordPress versions could mishandle an encoded colon in HTML, allowing unsafe protocol text to pass filtering. The main business concern is exposure on outdated WordPress sites, especially public sites with user-supplied content.

Executive priority

Treat this as a patch-compliance issue for legacy WordPress. It is not KEV-listed in the bundle, but public-facing outdated WordPress sites should be upgraded because sanitization bypasses can affect site integrity and visitor trust.

Technical view

The issue is in wp_kses_bad_protocol in wp-includes/kses.php before WordPress 5.3.1. It mishandles the HTML5 colon named entity, allowing bad-protocol filtering to be bypassed with encoded protocol text. The source bundle does not provide CVSS, CWE, or a complete affected-version matrix beyond WordPress before 5.3.1.

Likely exposure

Exposure is most likely on WordPress installations older than 5.3.1, including systems using affected Debian WordPress packages before the referenced security updates. Sites accepting or rendering user-controlled HTML are the priority to review.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation. The CVE description documents a sanitization bypass pattern, but the bundle does not provide exploit prevalence, attacker maturity, or confirmed real-world use.

Researcher notes

Evidence is strongest for the root cause and fixed version. The bundle lacks CVSS, CWE, detailed exploitability, role requirements, and confirmed attack reports. Avoid assuming active exploitation or broader affected products beyond WordPress before 5.3.1 and referenced Debian packages.

Mitigation direction

  • Upgrade WordPress to 5.3.1 or later.
  • Apply Debian WordPress security updates where using Debian packages.
  • Review vendor guidance for any backported package fixes.
  • Restrict untrusted HTML input until patched.
  • Prioritize internet-facing and multi-author WordPress sites.

Validation and detection

  • Inventory WordPress versions across public and internal sites.
  • Confirm wp-includes/kses.php comes from a patched release or package.
  • Check Debian hosts against DSA-4599, DLA-2067-1, and DSA-4677.
  • Review change records for WordPress updates after December 2019.
  • Verify no unsupported WordPress instances remain online.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2019-20041 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.