How severe is CVE-2026-34481?

No CVSS score has been assigned to CVE-2026-34481 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-34481?

CVE-2026-34481 affects the following packages: org.apache.logging.log4j:log4j-layout-template-json (Maven), org.apache.logging.log4j:log4j-layout-template-json (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-34481?

Update org.apache.logging.log4j:log4j-layout-template-json to 2.25.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34481 is resolved across your whole dependency graph.

How do I detect CVE-2026-34481 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.logging.log4j:log4j-layout-template-json, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-34481 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-34481 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34481 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-34481?

CVE-2026-34481 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 54th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-34481?

CVE-2026-34481 is classified as CWE-116 (CWE-116). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-34481 published, and has it been updated?

CVE-2026-34481 was published on April 10, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2026-34481 — log4j-layout-template-json

Fix: apache/logging-log4j2#4080

CVE-2026-34481 is a CWE-116 vulnerability in org.apache.logging.log4j:log4j-layout-template-json. A fix is available for org.apache.logging.log4j:log4j-layout-template-json — see the affected versions and patch details below.

Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout

Also known asGHSA-w35j-pv5h-q9q9

Published

Apr 10, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

1 / 2

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34481.

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk+0.03%

Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected

☕org.apache.logging.log4j:log4j-layout-template-json☕org.apache.logging.log4j:log4j-layout-template-json

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

An attacker can exploit this issue only if both of the following conditions are met:

The application uses JsonTemplateLayout.
The application logs a MapMessage, or logs an object directly (e.g., via Logger.info(Object), which wraps it in an ObjectMessage), where the message contains an attacker-controlled floating-point value.

Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue.

Note: The fix released in version 2.25.4 did not cover all affected code paths. CVE-2026-49844 was assigned to the remaining issue, which concerns the MapMessage.asJson() serialization in Apache Log4j API and is fixed in versions 2.25.5 and 2.26.1.

Affected Packages

2 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.logging.log4j:log4j-layout-template-json`	≥ 2.14.0&&< 2.25.4	2.25.4`org.apache.logging.log4j:log4j-layout-template-json:2.25.4`
☕Maven	`org.apache.logging.log4j:log4j-layout-template-json`	≥ 3.0.0-alpha1	No fix

Affected Products

1 product · 7 configurations

Application

log4japache

≥ 2.14.0 && < 2.25.4

1 version

3.0.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.logging.log4j:log4j-layout-template-json, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.apache.logging.log4j:log4j-layout-template-json to 2.25.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34481 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

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.

Workaround published by Red Hat

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.

Source: Red Hat security advisory for CVE-2026-34481 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat AMQ Broker 7.13.6	`log4j-layout-template-json`	RHSA-2026:66545
Red Hat AMQ Broker 7.14.1	`log4j-layout-template-json`	RHSA-2026:66488
Red Hat build of Apache Camel 4.18.1.P1 for Spring Boot 3.5.16	`log4j-layout-template-json`	RHSA-2026:37390
Red Hat Data Grid 8.6.1	`log4j-layout-template-json`	RHSA-2026:22619
Streams for Apache Kafka 3.2.1	`log4j-layout-template-json`	RHSA-2026:54435
Red Hat Offline Knowledge Portal 1.2.13	`offline-knowledge-portal/rhokp-rhel9:1779996999`	RHSA-2026:21773

Frequently Asked Questions

Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in versions up to and including 2.25.3, produces invalid JSON output when log events contain non-finite floating-point values (NaN, Infinity, or -Infinity), which are prohibited by RFC 8259. This may cause downstream log processing systems to reject or fail to index affected records. An attacker can exploit this issue only if both of the following conditions are met: * The application uses JsonTemplateLayout. * The application logs a MapMessage, or logs an object directly (e.g., v

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