CVE-2018-20149

WordPress Core < 5.0.1 - Stored Cross-Site Scripting via File Uploads

2018-12-12 00:00

Strategic Overview

Status: Patched in 3.7.28
Affected Core: WordPress 5.0
Affected Version: 3.7 – 5.0 · 15 branches
CVSS: 6.4Medium
Weakness type: CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE: CVE-2018-20149

At a glance

CVE-2018-20149 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the WordPress 5.0 WordPress release line, affecting 3.7 – 5.0 · 15 branches. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). The issue is fixed in version 3.7.28; sites on affected versions should update now. Disclosed December 2018, reported by Tim Coen.

Vulnerability Overview

In WordPress before 4.9.9 and 5.x before 5.0.1, when the Apache HTTP Server is used, authors could upload crafted files that bypass intended MIME type restrictions, leading to XSS, as demonstrated by a .jpg file without JPEG data.

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 5.0 3.7 – 5.0 · 15 branches takes a caller who can reach the endpoint. 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 5.0 the fix is 3.7.28: builds 3.7 – 5.0 · 15 branches are affected, anything from 3.7.28 onward is not.

Remediation

Update to one of the following versions, or a newer patched version: 3.7.28, 3.8.28, 3.9.26, 4.0.25, 4.1.25, 4.2.22, 4.3.18, 4.4.17, 4.5.16, 4.6.13, 4.7.12, 4.8.8, 4.9.9, 5.0.1

How does WordSec protect against this?

The attempt arrives as an ordinary request to WordPress 5.0: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: updating to 3.7.28 is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2018-20149 https://www.wordfence.com/threat-intel/vulnerabilities/id/4df635b8-4c56-4b24-8446-8e39e6fe7441 https://nvd.nist.gov/vuln/detail/CVE-2018-20149

Related records

Same weakness class

Other vulnerabilities in WordPress 5.0

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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