CVE-2018-1000773

WordPress Core < 5.0.1 - PHAR Unserialization

2018-09-06 00:00

Strategic Overview

Status: Patched in 3.7.28
Affected Core: WordPress 5.0
Affected Version: 3.7 – 5.0 · 15 branches
CVSS: 7.5High
Weakness type: CWE-502 · Deserialization of Untrusted Data
CVE: CVE-2018-1000773

At a glance

CVE-2018-1000773 is a high-severity Deserialization of Untrusted Data vulnerability in the WordPress 5.0 WordPress release line, affecting 3.7 – 5.0 · 15 branches. It carries a CVSS score of 7.5 (reachable over the network; high confidentiality, integrity, availability impact). The issue is fixed in version 3.7.28; sites on affected versions should update now. Disclosed September 2018, reported by Sam Thomas.

Vulnerability Overview

WordPress Core versions before 5.0.1 contain a CWE-20 Input Validation vulnerability in thumbnail processing that can result in remote code execution due to an incomplete fix for CVE-2017-1000600. This attack appears to be exploitable via thumbnail upload by an authenticated user and may require additional plugins in order to be exploited however this has not been confirmed at this time.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.

CWE-502: Deserialization of Untrusted Data

Reaching this weakness in WordPress 5.0 3.7 – 5.0 · 15 branches takes a caller who can reach the endpoint. Deserialization of untrusted data means the application reconstructs objects from input a caller controls, letting the attacker choose which classes get instantiated and what their properties hold.

A workable chain turns deserialization into file writes, deletions or code execution, depending on what the loaded classes do in their magic methods. 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. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: updating to 3.7.28 is the step that ends it.

Firewall
Scanner
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2018-1000773 https://www.wordfence.com/threat-intel/vulnerabilities/id/1f846ffa-0dfa-4549-845a-7884a390462a https://nvd.nist.gov/vuln/detail/CVE-2018-1000773

Related records

Same weakness class

Other vulnerabilities in WordPress 5.0

CVSS Vector

7.5

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

Base

Attack VectorNetwork
Attack ComplexityHigh
Privileges RequiredLow
User InteractionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh

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