Vulnerability in Apache Log4j
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…
EPSS: 0.001 (31.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
Affected products
- Apache Log4j — versions 3.0.0
- Apache Software Foundation Log4j 1 To 2 Bridge — versions 2.7, 3.0.0-alpha1
Weakness classification (CWE)
References
- security@apache.org (Exploit, Patch, patch, Issue Tracking)
- security@apache.org (vendor-advisory, Vendor Advisory)
- security@apache.org (vendor-advisory, Vendor Advisory)
- security@apache.org (related, Mitigation)
- security@apache.org (vendor-advisory, Mailing List)
- af854a3a-2127-422b-91ae-364da2661108 (Mailing List)
Frequently asked questions
- What is CVE-2026-34479?
- CVE-2026-34479 is a high-severity vulnerability in Apache Log4j, classified under Improper Encoding or Escaping of Output. CVSS score: 7.5/10. Published 2026-04-10.
- How severe is CVE-2026-34479?
- High severity. CVSS v3 base score is 7.5 out of 10.