CVE-2026-40023

MEDIUM EPSS 39.0%
Published Apr 10, 20262mo ago · Modified Jun 17, 20262w ago
6.3 CVSS 4.0
Medium
Find Similar
Published Apr 10, 2026 2mo ago
Last Modified Jun 17, 2026 2w ago

Description

Apache Log4cxx's XMLLayout https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html , in versions before 1.7.0, fails to sanitize characters forbidden by the XML 1.0 specification https://www.w3.org/TR/xml/#charsets in log messages, NDC, and MDC property keys and values, producing invalid XML output. Conforming XML parsers must reject such documents with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records. An attacker who can influence logged data can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity. Users are advised to upgrade to Apache Log4cxx 1.7.0, which fixes this issue.

CVSS Details

Base Score
6.3
Exploitability
—
Impact
—
Vector string
CVSS:4.0/AV:N/AC:H/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
Attack Vector Network
Attack Complexity High
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
39.0% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-116

Affected Products 1

VendorProductVersionRange
apachelog4cxx* <1.7.0

References 6

  • openwall.com http://www.openwall.com/lists/oss-security/2026/04/10/12
    Mailing ListThird Party Advisory
  • github.com https://github.com/apache/logging-log4cxx/pull/609
    Issue TrackingPatch
  • lists.apache.org https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b
    Mailing ListVendor Advisory
  • logging.apache.org https://logging.apache.org/cyclonedx/vdr.xml
    Product
  • logging.apache.org https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html
    Product
  • logging.apache.org https://logging.apache.org/security.html#CVE-2026-40023
    Vendor Advisory

Remediation

  • github.com https://github.com/apache/logging-log4cxx/pull/609
    Issue TrackingPatch