CVE-2016-5836

WordPress Core < 4.5.3 - Denial of Service via oEmbed Protocol

2016-06-18 00:00

Strategic Overview

Status: Patched in 3.7.15
Affected Core: WordPress 4.5
Affected Version: 3.7 – 4.5.2 · 10 branches
CVSS: 5.3Medium
Weakness type: CWE-400 · Uncontrolled Resource Consumption
CVE: CVE-2016-5836

At a glance

CVE-2016-5836 is a medium-severity Uncontrolled Resource Consumption vulnerability in the WordPress 4.5 WordPress release line, affecting 3.7 – 4.5.2 · 10 branches. It carries a CVSS score of 5.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 3.7.15; sites on affected versions should update now. Disclosed June 2016, reported by Jennifer Dodd.

Vulnerability Overview

The oEmbed protocol implementation in WordPress before 4.5.3 allows remote attackers to cause a denial of service via unspecified vectors.

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.

CWE-400: Uncontrolled Resource Consumption

Reaching this weakness in WordPress 4.5 3.7 – 4.5.2 · 10 branches 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 4.5 the fix is 3.7.15: builds 3.7 – 4.5.2 · 10 branches are affected, anything from 3.7.15 onward is not.

Remediation

Update to one of the following versions, or a newer patched version: 3.7.15, 3.8.15, 3.9.13, 4.0.12, 4.1.12, 4.2.9, 4.3.5, 4.4.4, 4.5.3

How does WordSec protect against this?

The attempt arrives as an ordinary request to WordPress 4.5: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: updating to 3.7.15 is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2016-5836 https://www.wordfence.com/threat-intel/vulnerabilities/id/17646179-47ad-4846-a581-3e713df43c32 https://nvd.nist.gov/vuln/detail/CVE-2016-5836

Related records

Same weakness class

Other vulnerabilities in WordPress 4.5

CVSS Vector

5.3

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

Base

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

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