CVE-2020-28039

WordPress Core < 5.5.2 - Arbitrary File Deletion

2020-10-29 00:00

Strategic Overview

Status: Patched in 3.7.35
Affected Core: WordPress 5.5
Affected Version: 3.7 – 5.5.1 · 20 branches
CVSS: 5.4Medium
Weakness type: CWE-285 · Improper Authorization
CVE: CVE-2020-28039

At a glance

CVE-2020-28039 is a medium-severity Improper Authorization vulnerability in the WordPress 5.5 WordPress release line, affecting 3.7 – 5.5.1 · 20 branches. It carries a CVSS score of 5.4 (reachable over the network; low attack complexity). The issue is fixed in version 3.7.35; sites on affected versions should update now. Disclosed October 2020, reported by Slavco Mihajloski.

Vulnerability Overview

is_protected_meta in wp-includes/meta.php in WordPress before 5.5.2 allows arbitrary file deletion because it does not properly determine whether a meta key is considered protected.

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-285: Improper Authorization

Reaching this weakness in WordPress 5.5 3.7 – 5.5.1 · 20 branches takes a caller who can reach the endpoint. Improper authorization means a permission check exists but does not cover the case being exercised, so a caller who is allowed to do one thing is allowed to do a neighbouring thing as well.

A lower-privileged account performs an action reserved for a higher one, which on a multi-author or membership site means an ordinary user reaching administrative behaviour. For WordPress 5.5 the fix is 3.7.35: builds 3.7 – 5.5.1 · 20 branches are affected, anything from 3.7.35 onward is not.

Remediation

Update to one of the following versions, or a newer patched version: 3.7.35, 3.8.35, 3.9.33, 4.0.32, 4.1.32, 4.2.29, 4.3.25, 4.4.24, 4.5.23, 4.6.20, 4.7.19, 4.8.15, 4.9.16, 5.0.11, 5.1.7, 5.2.8, 5.3.5, 5.4.3, 5.5.2

How does WordSec protect against this?

Because it turns on account access, WordSec's login security is the relevant layer: role-based two-factor, captcha and brute-force limits raise the cost of getting the account this needs. None of that substitutes for the fix: updating to 3.7.35 is the step that ends it.

Login Security
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2020-28039 https://www.wordfence.com/threat-intel/vulnerabilities/id/beb70eb8-9a9c-4116-832c-337fc2a03329 https://nvd.nist.gov/vuln/detail/CVE-2020-28039

Related records

Same weakness class

Other vulnerabilities in WordPress 5.5

CVSS Vector

5.4

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

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredLow
User InteractionNone
ScopeUnchanged
ConfidentialityNone
IntegrityLow
AvailabilityLow

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