Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through 2.25.4 and version 2.26.0. The fix for CVE-2026-34481 did not cover all code paths: when a MapMessage contains a non-finite IEEE 754 value (NaN, Infinity, or -Infinity), MapMessage.asJson() emits the corresponding bare token. RFC 8259 does not permit these tokens, so a conformant parser rejects the resulting document. The defect is reachable only when both of the following conditions hold: * The application uses the message resolver https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message of JsonTemplateLayout or any other layout that relies on MapMessage.asJson() or MapMessage.getFormattedMessage(new String[]{"JSON"}). * The application logs a MapMessage that contains an attacker-controlled floating-point value. An attacker who can supply a non-finite value can cause the affected layout to emit malformed JSON, which may corrupt the enclosing log record or disrupt downstream log ingestion and parsing. Users are advised to upgrade to Apache Log4j API 2.25.5 or 2.26.1, both of which emit RFC 8259-compliant JSON for non-finite values.

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-099531 advisory.

    Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j     API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through     2.25.4 and version 2.26.0.

    The fix for CVE-2026-34481 did not cover all code paths: when a MapMessage contains a non-finite IEEE 754     value (NaN, Infinity, or -Infinity), MapMessage.asJson() emits the corresponding bare token. RFC 8259 does     not permit these tokens, so a conformant parser rejects the resulting document.

    The defect is reachable only when both of the following conditions hold:

      *  The application uses the  message resolver https://logging.apache.org/log4j/2.x/manual/json-template-     layout.html#event-template-resolver-message  of JsonTemplateLayout or any other layout that relies on     MapMessage.asJson() or MapMessage.getFormattedMessage(new String[]{JSON}).
      *  The application logs a MapMessage that contains an attacker-controlled floating-point value.


    An attacker who can supply a non-finite value can cause the affected layout to emit malformed JSON, which     may corrupt the enclosing log record or disrupt downstream log ingestion and parsing.

    Users are advised to upgrade to Apache Log4j API 2.25.5 or 2.26.1, both of which emit RFC 8259-compliant     JSON for non-finite values.

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j
    API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through
    2.25.4 and version 2.26.0. The fix for CVE-2026-34481 did not cover all code paths: when a MapMessage
    contains a non-finite IEEE 754 value (NaN, Infinity, or -Infinity), MapMessage.asJson() emits the
    corresponding bare token. RFC 8259 does not permit these tokens, so a conformant parser rejects the
    resulting document. The defect is reachable only when both of the following conditions hold: * The
    application uses the message resolver https://logging.apache.org/log4j/2.x/manual/json-template-
    layout.html#event-template-resolver-message of JsonTemplateLayout or any other layout that relies on
    MapMessage.asJson() or MapMessage.getFormattedMessage(new String[]{"JSON"}). * The application logs a
    MapMessage that contains an attacker-controlled floating-point value. An attacker who can supply a non-
    finite value can cause the affected layout to emit malformed JSON, which may corrupt the enclosing log
    record or disrupt downstream log ingestion and parsing. Users are advised to upgrade to Apache Log4j API
    2.25.5 or 2.26.1, both of which emit RFC 8259-compliant JSON for non-finite values. (CVE-2026-49844)

The version of Apache Log4j on the remote host is affected by a vulnerability:

  - Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j     API produces output that is not valid JSON. When a MapMessage contains a non-finite IEEE 754 value (NaN,     Infinity, or -Infinity), MapMessage.asJson() emits the corresponding bare token. RFC 8259 does not permit     these tokens, so a conformant parser rejects the resulting document. An attacker who can supply a non-finite     value can cause the affected layout to emit malformed JSON, which may corrupt the enclosing log record or     disrupt downstream log ingestion and parsing. (CVE-2026-49844)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j     API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through     2.25.4 and version 2.26.0. The fix for CVE-2026-34481 did not cover all code paths: when a MapMessage     contains a non-finite IEEE 754 value (NaN, Infinity, or -Infinity), MapMessage.asJson() emits the     corresponding bare token. RFC 8259 does not permit these tokens, so a conformant parser rejects the     resulting document. The defect is reachable only when both of the following conditions hold: * The     application uses the message resolver https://logging.apache.org/log4j/2.x/manual/json-template-     layout.html#event-template-resolver-message of JsonTemplateLayout or any other layout that relies on     MapMessage.asJson() or MapMessage.getFormattedMessage(new String[]{JSON}). * The application logs a     MapMessage that contains an attacker-controlled floating-point value. An attacker who can supply a non-     finite value can cause the affected layout to emit malformed JSON, which may corrupt the enclosing log     record or disrupt downstream log ingestion and parsing. Users are advised to upgrade to Apache Log4j API     2.25.5 or 2.26.1, both of which emit RFC 8259-compliant JSON for non-finite values. (CVE-2026-49844)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
336926	Unity Linux 20.1070e Security Update: log4j (UTSA-2026-099531)	Nessus	Unity Linux Local Security Checks	Local	medium
445957	SCA: security update for org.apache.logging.log4j:log4j-api (GHSA-qv9r-c865-cp47)	Tenable Cloud Security	SCA Checks	Local	medium
445957	SCA: security update for org.apache.logging.log4j:log4j-api (GHSA-qv9r-c865-cp47)	Tenable Self-Hosted Container Security	SCA Checks	Local	medium
327598	Apache Log4j 2.13.1 < 2.25.5 / 2.26.0 < 2.26.1 Improper JSON Serialization (CVE-2026-49844)	Nessus	Misc.	Local	medium
326435	Linux Distros Unpatched Vulnerability : CVE-2026-49844	Nessus	Misc.	Local	medium

Detections

Analytics

CVE-2026-49844

medium

Tenable Plugins

medium

medium

medium

medium

medium