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No exploitation reportedFix available

CVE-2026-34479

No exploitation reported by the sources we read.

  • Published2026-04-10
  • Fixed in2.25.4
  • WeaknessCWE-116

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

The Log4j1XmlLayout from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML 1.0 standard, producing malformed XML output. Conforming XML parsers are required to reject documents containing such characters with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. Two groups of users are affected: * Those using Log4j1XmlLayout directly in a Log4j Core 2 configuration file. * Those using the Log4j 1 configuration compatibility layer with org.apache.log4j.xml.XMLLayout specified as the layout class. Users are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue. Note: The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the Log4j 1 to Log4j 2 migration guide https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html , and specifically the section on eliminating reliance on the bridge.

Timeline

dates in UTC
  1. 2026-04-1016:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-34479?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-34479?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Apache Log4j
BranchAffectedFixed in
2.x≥ 2.7, < 2.25.42.25.4
3.0= 3.0.0no fix published
3.0≥ 3.0.0-beta1, ≤ 3.0.0-beta2no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As apache, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Apache Software Foundation Apache Log4j 1 to Log4j 2 bridgeother versions: not affected

    package org.apache.logging.log4j:log4j-1.2-apihttps://repo.maven.apache.org/maven2

    Affected
    • ≥ 2.7, < 2.25.4fixed in 2.25.4maven
    • ≥ 3.0.0-alpha1, ≤ 3.0.0-beta2no fix statedmaven

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-04-10

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • airflow-3MinimOSall versions · fixed in 3.3.2-r0
  • akhqWolfiall versions · fixed in 0.27.0-r2
  • akhqMinimOSall versions · fixed in 0.28.0-r0and 1 other package
  • akhqCleanStartall versions · fixed in 0.27.1-r5
  • akhqChainguardall versions · fixed in 0.27.0-r2
  • apache-activemq-5.19MinimOSall versions · fixed in 5.19.10-r0and 1 other package
  • apache-activemq-6.2MinimOSall versions · fixed in 6.2.8-r0and 1 other package
  • apache-druidMinimOSall versions · fixed in 38.0.0-r0and 1 other package

156 more package ranges on OSV.dev

Vendor advisories

  • CVE-2026-34479 Red Hat Product Security2 products fixed · 16 known affected

    org.apache.logging.log4j/log4j-1.2-api: Apache Log4j 1-to-Log4j 2 bridge: Log processing denial of service due to improper XML escaping

    log4j-1.2-api as a component of Red Hat Data Grid 8 · log4j as a component of Red Hat Enterprise Linux 8 · log4j-jcl as a component of Red Hat Enterprise Linux 8 · +13 more

  • RHSA-2026:21773 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: Red Hat Offline Knowledge Portal security and content update

Full record on NVD

Fix

  1. Update Apache Log4j to 2.25.4
  2. Vendor fix Red Hat Product Security RHSA-2026:21773 · 2 productsThe container image provided by this update can be downloaded from the Red Hat container registry at registry.redhat.io using the "podman pull" command.
  3. Workaround from the vendor Red Hat Product Security RHSA-2026:21773 · 2 productsMitigation 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.
  4. No fix available, says the vendor Red Hat Product Security CVE-2026-34479 · 13 productsFix deferred
  5. No fix planned, says the vendor Red Hat Product Security CVE-2026-34479 · 3 productsOut of support scope

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS 4.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Published
2026-04-10
Last Modified
2026-10-26
NVD status
Analyzed
MSRC Title
Apache Log4j 1 to Log4j 2 bridge: Silent log event loss in Log4j1XmlLayout due to unescaped XML 1.0 forbidden characters
GitHub Advisory
GHSA-h383-gmxw-35v2

Frequently asked questions

What is CVE-2026-34479?

The Log4j1XmlLayout from the Apache Log4j 1-to-Log4j 2 bridge fails to escape characters forbidden by the XML 1.0 standard, producing malformed XML output. Conforming XML parsers are required to reject documents containing such characters with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. Two groups of users are affected: * Those using Log4j1XmlLayout directly in a Log4j Core 2 configuration file. * Those using the Log4j 1 configuration compatibility layer with org.apache.log4j.xml.XMLLayout specified as the layout class. Users are advised to upgrade to Apache Log4j 1-to-Log4j 2 bridge version 2.25.4, which corrects this issue. Note: The Apache Log4j 1-to-Log4j 2 bridge is deprecated and will not be present in Log4j 3. Users are encouraged to consult the Log4j 1 to Log4j 2 migration guide https://logging.apache.org/log4j/2.x/migrate-from-log4j1.html , and specifically the section on eliminating reliance on the bridge.

Is CVE-2026-34479 actively exploited?

Active exploitation of CVE-2026-34479 has not been confirmed. Its EPSS score was 0.5% on 2026-11-03, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-34479?

CVE-2026-34479 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

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