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Fencer Vulns
high 7.5

CVE-2026-34478 json

Apache Log4j Core: Log injection in Rfc5424Layout due to silent configuration incompatibility

published 2026-04-10 6 mo ago modified 2026-10-26 13 d ago also GHSA-445c-vh5m-36rj , EUVD-2026-21408

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 62%
public exploits
0
none known

Summary

Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in versions 2.21.0 through 2.25.3, is vulnerable to log injection via CRLF sequences due to undocumented renames of security-relevant configuration attributes.

Two distinct issues affect users of stream-based syslog services who configure Rfc5424Layout directly:

* The newLineEscape attribute was silently renamed, causing newline escaping to stop working for users of TCP framing (RFC 6587), exposing them to CRLF injection in log output. * The useTlsMessageFormat attribute was silently renamed, causing users of TLS framing (RFC 5425) to be silently downgraded to unframed TCP (RFC 6587), without newline escaping.

Users of the SyslogAppender are not affected, as its configuration attributes were not modified.

Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.

Patch / fix

  • maven org.apache.logging.log4j:log4j-core 2.25.4
  • Apache Software Foundation Apache Log4j Core 2.25.4

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-34478 updated cvss 5.8

org.apache.logging.log4j/log4j-core: Apache Log4j Core: Log injection via CRLF sequences due to configuration attribute renames

  • Red Hat AI Inference Server redhat-user-workloads/ai-tenant/rhaiis-3-3/rhaiis-cuda-ubi9-3-3 Red Hat build of Apicurio Registry 2 log4j-core Red Hat build of Apicurio Registry 3 log4j-core
    affected: workaround, no fix planned “Will not fix”
  • Red Hat build of OptaPlanner 8 log4j-core
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 9 log4j, log4j-jcl, log4j-slf4j
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux AI (RHEL AI) 3 bazel7, bazel8, rhelai3/bootc-cuda-rhel9, redhat-user-workloads/rhel-ai-tenant/rhelai-bootc-3-3/bootc-cuda-aws-3-3, redhat-user-workloads/rhel-ai-tenant/rhelai-bootc-3-3/bootc-cuda-gcp-3-3, redhat-user-workloads/rhel-ai-tenant/rhelai-bootc-3-3/bootc-cuda-azure-3-3
    affected: workaround, no fix available
  • Red Hat JBoss Enterprise Application Platform 7 log4j-core
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Offline Knowledge Portal redhat-user-workloads/rhocc-mimir-tenant/mimir/rhokp-core-encrypted
    affected: workaround, no fix available
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-pipeline-runtime-pytorch-cuda-py312-rhel9, rhoai/odh-pipeline-runtime-pytorch-rocm-py312-rhel9, rhoai/odh-workbench-jupyter-pytorch-cuda-py312-rhel9, rhoai/odh-workbench-jupyter-pytorch-rocm-py312-rhel9, rhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9, rhoai/odh-pipeline-runtime-datascience-cpu-py312-rhel9, +5 more Red Hat streams for Apache Kafka 2 log4j-core
    affected: workaround, no fix planned “Will not fix”
  • Red Hat HawtIO HawtIO 4.4.0
    fixed: vendor fix RHSA-2026:25089
show 13 more
  • Red Hat AMQ Broker 7.13.6
    fixed: vendor fix RHSA-2026:66545
  • Red Hat AMQ Broker 7.14.1
    fixed: vendor fix RHSA-2026:66488
  • Red Hat build of Apache Camel 4.18.1.P1 for Spring Boot 3.5.16
    fixed: vendor fix RHSA-2026:37390
  • Red Hat Data Grid 8.6.1
    fixed: vendor fix RHSA-2026:22619
  • Red Hat Offline Knowledge Portal 1.2.13 offline-knowledge-portal/rhokp-rhel9 1779996999
    fixed: vendor fix RHSA-2026:21773
  • Red Hat OpenShift AI 2.25 rhoai/odh-modelmesh-rhel9 1783443816
    fixed: vendor fix RHSA-2026:42644
  • Red Hat Streams for Apache Kafka 3.2.1
    fixed: vendor fix RHSA-2026:54435
  • Red Hat AI Inference Server redhat-user-workloads/ai-tenant/rhaiis-3-2-2/rhaiis-cuda-ubi9-3-2-2 Red Hat Enterprise Linux 8 log4j, resteasy, log4j-jcl, log4j-web, log4j-slf4j, resteasy-javadoc
    not affected: vulnerable code not present
  • Red Hat Enterprise Linux 9 resteasy, pki-resteasy-core, pki-resteasy-client, pki-resteasy-jackson2-provider, pki-resteasy-servlet-initializer
    not affected: component not present
  • Red Hat Fuse 7 log4j-core
    not affected: vulnerable code not in execute path
  • Red Hat JBoss Enterprise Application Platform 8 log4j-core, log4j-core-test Red Hat JBoss Enterprise Application Platform Expansion Pack log4j-core, log4j-core-test
    not affected: vulnerable code not present
  • Red Hat JBoss Web Server 6 log4j-core
    not affected: component not present
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-modelmesh-rhel8, rhoai/odh-vllm-cuda-rhel9, rhoai/odh-vllm-gaudi-rhel9 Red Hat OpenShift AI 2.25 rhoai/odh-rhel9-operator 1784004914, rhoai/odh-vllm-cpu-rhel9 1782397826, rhoai/odh-dashboard-rhel9 1782826282, rhoai/odh-operator-bundle 1784005555, rhoai/odh-vllm-cuda-rhel9 1783998774, rhoai/odh-vllm-rocm-rhel9 1783998857, +69 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.99% chance of exploitation in the next 30 days, higher than 62% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.9 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
CNA 4.0 6.9 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
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
maven org.apache.logging.log4j:log4j-core
>=2.21.0, <2.25.4
>=3.0.0-beta1, <=3.0.0-beta3
2.25.4

Affected products

  • Apache Software Foundation Apache Log4j Core

Classification

Weakness
  • CWE-684 Incorrect Provision of Specified Functionality
  • CWE-117 Improper Output Neutralization for Logs
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.