6.3

CVE-2026-34477: apache software foundation apache log4j core

CVSS: 6.3v4.0MediumAnalyzed
AliasesUBUNTU-CVE-2026-34477CGA-24j8-94m5-gh85CGA-25m6-7825-6v66
Published 10-04-2026Last modified 10-04-2026
Open JSON

Vulnerability summary

CVE-2026-34477 is a medium (CVSS 6.3) vulnerability in apache software foundation apache log4j core. EPSS estimates a 0.50% chance of exploitation in the next 30 days, higher than 41.6% of scored vulnerabilities.

Overall risk
25/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.50%
0%100%
Low · +0.09 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 1 · Related 2
OPENSUSE-SU-2026:10544-1CGA-99GG-5485-CVHJ

Timeline

  1. 10-04-2026
    PublishedVulnerability first disclosed.
  2. 10-04-2026
    Last modifiedVulnerability information updated.

Description

The fix for CVE-2025-68161 https://logging.apache.org/security.html#CVE-2025-68161 was incomplete: it addressed hostname verification only when enabled via the log4j2.sslVerifyHostName https://logging.apache.org/log4j/2.x/manual/systemproperties.html#log4j2.sslVerifyHostName system property, but not when configured through the verifyHostName https://logging.apache.org/log4j/2.x/manual/appenders/network.html#SslConfiguration-attr-verifyHostName attribute of the <Ssl> element. Although the verifyHostName configuration attribute was introduced in Log4j Core 2.12.0, it was silently ignored in all versions through 2.25.3, leaving TLS connections vulnerable to interception regardless of the configured value. A network-based attacker may be able to perform a man-in-the-middle attack when all of the following conditions are met: * An SMTP, Socket, or Syslog appender is in use. * TLS is configured via a nested <Ssl> element. * The attacker can present a certificate issued by a CA trusted by the appender's configured trust store, or by the default Java trust store if none is configured. This issue does not affect users of the HTTP appender, which uses a separate verifyHostname https://logging.apache.org/log4j/2.x/manual/appenders/network.html#HttpAppender-attr-verifyHostName attribute that was not subject to this bug and verifies host names by default. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.

CVSS metrics

8 scores · 6 sources · 2 versions

EPSS trend

Probability

0.50%

Chance of exploitation in the next 30 days

Percentile

42%

Versus all other CVEs

30-day change

+0.09 pp

From 0.41% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.50%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard146 products
  • airflow-2All versions (No fix recorded)
  • airflow-3< 3.2.1-r1
  • akhq< 0.27.0-r2
  • apache-activemq-5.19< 5.19.6-r2
  • apache-activemq-6.1< 6.1.8-r3
Wolfi39 products
  • airflow-3< 3.2.1-r1
  • akhq< 0.27.0-r2
  • apache-activemq-artemis< 2.53.0-r5
  • apache-pulsar-4.1All versions (No fix recorded)
  • apache-pulsar-4.2< 4.2.1-r0
Apache1 product
  • log4j≥ 2.12.0, < 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
Apache software foundation1 product
Org.apache.logging.log4j1 product
  • log4j-core≥ 2.12.0, < 2.25.4 | ≥ 3.0.0-alpha1, ≤ 3.0.0-beta3
Ubuntu1 product
  • apache-log4j2All versions (No fix recorded)

6 vendors · 189 products

References

11 links
Show all 11 references