Vulnerability in Apache Software Foundation Apache Log4j JSON Template Layout

[ Description ]Official description

Apache Log4j's JsonTemplateLayout https://logging.apache.org/log4j/2.x/manual/json-template-layout.html , in versions up to and including 2.25.3, produces invalid JSON output when log events contain non-finite floating-point values (NaN, Infinity, or -Infinity), which are prohibited by RFC 8259. This may cause downstream log processing systems to reject or fail to index affected records. An attacker can exploit this issue only if both of the following conditions are met: * The application uses JsonTemplateLayout. * The application logs a MapMessage, or logs an object directly (e.g., via Logger.info(Object), which wraps it in an ObjectMessage), where the message contains an attacker-controlled floating-point value. Users are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue. Note: The fix released in version 2.25.4 did not cover all affected code paths. CVE-2026-49844 was assigned to the remaining issue, which concerns the MapMessage.asJson() serialization in Apache Log4j API and is fixed in versions 2.25.5 and 2.26.1.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund20 Oct 2026WID-SEC-2026-4090

  Oracle Communications: Multiple vulnerabilities Translated from German

  Risk highCVE-2026-101763CVE-2026-58389CVE-2026-56740+85 more CVEs
• BSI CERT-Bund20 Oct 2026WID-SEC-2026-4083

  Oracle Retail Applications: Multiple vulnerabilities Translated from German

  Risk highCVE-2026-34481CVE-2026-41855CVE-2026-59901+1 more CVEs
• CERT-FR16 Oct 2026CERTFR-2026-AVI-1336

  Multiple vulnerabilities in IBM products Translated from French

  Multiple vulnerabilities have been discovered in IBM products. Some of them allow an attacker to cause remote arbitrary code execution, privilege escalation and remote denial of service.

  CVE-2026-14671CVE-2026-11548CVE-2022-22950+490 more CVEs
• CERT-FR9 Oct 2026CERTFR-2026-AVI-1291

  Multiple vulnerabilities in IBM products Translated from French

  Multiple vulnerabilities have been discovered in IBM products. Some of them allow an attacker to cause remote arbitrary code execution, privilege escalation and remote denial of service.

  CVE-2026-49978CVE-2025-27895CVE-2026-59651+195 more CVEs
• CERT-FR2 Oct 2026CERTFR-2026-AVI-1256

  Multiple vulnerabilities in IBM products Translated from French

  Multiple vulnerabilities have been discovered in IBM products. Some of them allow an attacker to cause remote arbitrary code execution, privilege escalation and remote denial of service.

  CVE-2026-27980CVE-2026-58055CVE-2026-49978+360 more CVEs

[ References ]References

• github.com/apache/logging-log4j2/pull/4080patch
• logging.apache.org/security.htmlvendor-advisory
• logging.apache.org/cyclonedx/vdr.xmlvendor-advisory
• logging.apache.org/log4j/2.x/manual/json-template-layout.htmlrelated
• lists.apache.org/thread/n34zdv00gbkdbzt2rx9rf5mqz6lhopcvvendor-advisory