Detections
Analytics

Apache Log4j 2.0-alpha1 < 2.25.4 XmlLayout Invalid XML Output (CVE-2026-34480)

medium Nessus Plugin ID 306549

Synopsis

A logging library installed on the remote host is affected by an improper output encoding vulnerability.

Description

The version of Apache Log4j on the remote host is 2.0-alpha1 through 2.25.3. It is, therefore, affected by a vulnerability:

 - The XmlLayout fails to sanitize characters forbidden by the XML 1.0 specification, producing invalid XML output whenever a log message or MDC value contains such characters. Depending on the StAX implementation, this causes either malformed XML or exceptions during logging. (CVE-2026-34480)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Apache Log4j version 2.25.4 or later.

See Also

https://logging.apache.org/security.html

Plugin Details

Severity: Medium

ID: 306549

File Name: apache_log4j_CVE-2026-34480.nasl

Version: 1.1

Type: Local

Agent: windows, macosx, unix

Family: Misc.

Published: 4/15/2026

Updated: 4/15/2026

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.8

CVSS v2

Risk Factor: Medium

Base Score: 5

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:N

CVSS Score Source: CVE-2026-34480

CVSS v3

Risk Factor: Medium

Base Score: 5.8

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

CVSS v4

Risk Factor: Medium

Base Score: 6.9

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

Vulnerability Information

CPE: cpe:/a:apache:log4j

Required KB Items: installed_sw/Apache Log4j

Patch Publication Date: 4/10/2026

Vulnerability Publication Date: 4/10/2026

Reference Information

CVE: CVE-2026-34480