CVE-2021-29447

WordPress Core < 5.7.1 - XXE Injection

2021-04-15 00:00

Strategic Overview

Status: Patched in 4.7.20
Affected Core: WordPress 5.7
Affected Version: 4.7 – < 5.7.1 · 11 branches
CVSS: 7.1High
Weakness type: CWE-611 · Improper Restriction of XML External Entity Reference
CVE: CVE-2021-29447

At a glance

CVE-2021-29447 is a high-severity Improper Restriction of XML External Entity Reference vulnerability in the WordPress 5.7 WordPress release line, affecting 4.7 – < 5.7.1 · 11 branches. It carries a CVSS score of 7.1 (reachable over the network; low attack complexity; high confidentiality impact). The issue is fixed in version 4.7.20; sites on affected versions should update now. Disclosed April 2021, reported by SonarSource.

Vulnerability Overview

Wordpress is an open source CMS. A user with the ability to upload files (like an Author) can exploit an XML parsing issue in the Media Library leading to XXE attacks. This requires WordPress installation to be using PHP 8. Access to internal files is possible in a successful XXE attack. This has been patched in WordPress version 5.7.1, along with the older affected versions via a minor release. We strongly recommend you keep auto-updates enabled.

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. A successful exploit has high impact on confidentiality.

CWE-611: Improper Restriction of XML External Entity Reference

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

Remediation

Update to one of the following versions, or a newer patched version: 4.7.20, 4.8.16, 4.9.17, 5.0.12, 5.1.9, 5.2.10, 5.3.7, 5.4.5, 5.5.4, 5.6.3, 5.7.1

How does WordSec protect against this?

The attempt arrives as an ordinary request to WordPress 5.7: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: updating to 4.7.20 is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2021-29447 https://www.wordfence.com/threat-intel/vulnerabilities/id/9df45c8e-c040-4031-9c51-4c43d12f08b0 https://nvd.nist.gov/vuln/detail/CVE-2021-29447

Related records

Same weakness class

Other vulnerabilities in WordPress 5.7

CVSS Vector

7.1

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

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredLow
User InteractionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityLow
AvailabilityNone

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