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CVE-2026-34481

org.apache.logging.log4j: Apache Log4j JsonTemplateLayout: Denial of Service via invalid JSON output

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Severity

Moderate

Red Hat Product Security

6.5

CVSS 3.1

Review impact separately from score.

Published · April 11, 2026

Updated · October 10, 2026

Description

A flaw was found in Apache Log4j's JsonTemplateLayout. This vulnerability allows a remote attacker to disrupt log processing systems. By sending log events that include specific non-numeric floating-point values, the attacker can cause the JsonTemplateLayout to generate invalid JSON output. This invalid output can then lead to downstream systems rejecting or failing to index these logs, effectively causing a denial of service for log analysis.

Statement

Exploitation of this flaw requires an application to be configured with JsonTemplateLayout and to log attacker-controlled non-finite floating-point values within a MapMessage, which is not a default or common configuration in Red Hat products.

CVSS score applicability

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

CVSS / CWE

CVSS 3.1 · 6.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CWE-241 · Improper Handling of Unexpected Data Type