CVE-2019-20041

WordPress Core < 5.3.1 - Authenticated Stored Cross-Site Scripting

2019-12-13 00:00

Strategic Overview

Status: Patched in 3.7.32
Affected Core: WordPress 5.3
Affected Version: 3.7 – 5.3 · 18 branches
CVSS: 6.4Medium
Weakness type: CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE: CVE-2019-20041

At a glance

CVE-2019-20041 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the WordPress 5.3 WordPress release line, affecting 3.7 – 5.3 · 18 branches. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). Exploitation requires an authenticated account. The issue is fixed in version 3.7.32; sites on affected versions should update now. Disclosed December 2019, reported by WordPress.org Security Team.

Vulnerability Overview

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&colon; substring.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no interaction from a victim user.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Reaching this weakness in WordPress 5.3 3.7 – 5.3 · 18 branches takes any authenticated account. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For WordPress 5.3 the fix is 3.7.32: builds 3.7 – 5.3 · 18 branches are affected, anything from 3.7.32 onward is not.

Remediation

Update to one of the following versions, or a newer patched version: 3.7.32, 3.8.32, 3.9.30, 4.0.29, 4.1.29, 4.2.26, 4.3.22, 4.4.21, 4.5.20, 4.6.17, 4.7.16, 4.8.12, 4.9.13, 5.0.8, 5.1.4, 5.2.5, 5.3.1

How does WordSec protect against this?

The attempt arrives as an ordinary request to WordPress 5.3: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: updating to 3.7.32 is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2019-20041 https://www.wordfence.com/threat-intel/vulnerabilities/id/1bc0aa64-57a6-44ef-974a-70991cc3820f https://nvd.nist.gov/vuln/detail/CVE-2019-20041

Related records

Same weakness class

Other vulnerabilities in WordPress 5.3

CVSS Vector

6.4

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredLow
User InteractionNone
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone

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