CVE-2026-34481: Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in

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HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-34481 is a high-severity flaw (CVSS 7.5) affecting log4j. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 fo

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-116
Published	2026-04-10
Last modified	2026-10-26

Publisher (CNA): Apache Software Foundation · Vendor: apache

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-10 16:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

apache log4j UPGRADE

Affected: >= 2.14.0 and < 2.25.4 · 3.0.0 alpha1 · 3.0.0 alpha1_rc1 · 3.0.0 alpha1_rc2 · 3.0.0 beta1 · 3.0.0 beta2 · 3.0.0 beta3

Fixed in: 2.25.4

Safe to downgrade to: a release before 2.14.0

1. Check installed version

apt-cache policy log4j || rpm -q log4j || log4j --version

2. UPGRADE to 2.25.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade log4j

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade log4j

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.14.0 (Debian / Ubuntu)

apt-cache madison log4j sudo apt install log4j=<VERSION_BEFORE_2.14.0> sudo apt-mark hold log4j

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list log4j sudo dnf downgrade log4j-<VERSION_BEFORE_2.14.0> sudo dnf versionlock add log4j

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-34481?

log4j: upgrade to 2.25.4. Exact commands for each OS are on this page.

Is CVE-2026-34481 being exploited?

CVE-2026-34481 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-34481 affect?

CVE-2026-34481 affects log4j. Severity is high (CVSS 7.5). 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, I

How urgent is CVE-2026-34481?

Priority 49/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Apache Log4j vulnerabilities

Related CVEs

CVE-2026-34478 HIGH 7.5 UPGRADE Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in
CVE-2026-34480 HIGH 7.5 UPGRADE Apache Log4j Core's XmlLayout https://logging.apache.org/log4j/2.x/manual/layouts.html#XmlLayout , in version
CVE-2026-34477 MEDIUM 5.9 UPGRADE The fix for CVE-2025-68161 https://logging.apache.org/security.html#CVE-2025-68161 was incomplete: it addres
CVE-2026-34479 HIGH 7.5 UPGRADE The Log4j1XmlLayout from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML
CVE-2026-49844 MEDIUM 5.9 UPGRADE Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API

References

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