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Apache Log4j 2.21.0 < 2.25.4 Rfc5424Layout Log Injection (CVE-2026-34478)

medium Nessus Plugin ID 306548

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Synopsis

A logging library installed on the remote host is affected by a log injection vulnerability.

Description

The version of Apache Log4j on the remote host is 2.21.0 through 2.25.3. It is, therefore, affected by a vulnerability:

 - The Rfc5424Layout is vulnerable to log injection via CRLF sequences due to undocumented renames of security-relevant configuration attributes. The newLineEscape attribute was silently renamed, disabling newline escaping for TCP framing. The useTlsMessageFormat attribute was also renamed, causing TLS framing users to be silently downgraded to unframed TCP. (CVE-2026-34478)

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: 306548

File Name: apache_log4j_CVE-2026-34478.nasl

Version: 1.4

Type: Local

Agent: windows, macosx, unix

Family: Misc.

Published: 4/15/2026

Updated: 4/27/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

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

CVSS Score Source: CVE-2026-34478

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

CVSS v4

Risk Factor: Medium

Base Score: 6.9

Threat Score: 2.7

Threat Vector: CVSS:4.0/E:U

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

Exploit Ease: No known exploits are available

Patch Publication Date: 4/10/2026

Vulnerability Publication Date: 4/10/2026

Reference Information

CVE: CVE-2026-34478

IAVA: 2026-A-0324