CVE-2018-6389

WordPress Core < 5.0 - Denial of Service

2018-02-05 00:00

Strategic Overview

Status: Patched in 5.0
Affected Core: WordPress 5.0
Affected Version: < 5.0
CVSS: 7.5High
Weakness type: CWE-400 · Uncontrolled Resource Consumption
CVE: CVE-2018-6389

At a glance

CVE-2018-6389 is a high-severity Uncontrolled Resource Consumption vulnerability in the WordPress 5.0 WordPress release line, affecting < 5.0. It carries a CVSS score of 7.5 (reachable over the network; low attack complexity; high availability impact). Exploitation requires no authentication. The issue is fixed in version 5.0; sites on affected versions should update now. Disclosed February 2018, reported by Barak Tawily.

Vulnerability Overview

In WordPress before 5.0, unauthenticated attackers can cause a denial of service (resource consumption) by using the large list of registered .js files (from wp-includes/script-loader.php) to construct a series of requests to load every file many times. It looks like most of the slowness was due to forcing PHP to repeatedly compress the output scripts, which was addressed in 5.0.

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 privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on availability.

CWE-400: Uncontrolled Resource Consumption

Reaching this weakness in WordPress 5.0 < 5.0 takes a caller who can reach the endpoint. Uncontrolled resource consumption means a request can make the server do an amount of work it never bounds, because the size or repetition of the job is taken from the request rather than capped by the code.

A single caller can hold PHP workers, database connections or disk open long enough to slow the site for everyone, without needing any account or any other flaw. For WordPress 5.0 the fix is 5.0: builds < 5.0 are affected, anything from 5.0 onward is not.

Remediation

Update to version 5.0, or a newer patched version

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 5.0 is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2018-6389 https://www.wordfence.com/threat-intel/vulnerabilities/id/1d5987cd-1304-487c-8d1c-cab0510fbb84 https://nvd.nist.gov/vuln/detail/CVE-2018-6389

Related records

Same weakness class

Other vulnerabilities in WordPress 5.0

CVSS Vector

7.5

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

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh

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