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CVE-2026-49844 is an improper output-encoding vulnerability in Apache Log4j API MapMessage JSON serialization. MapMessage.asJson() emits non-finite IEEE 754 values—NaN, Infinity, and -Infinity—as bare tokens prohibited by RFC 8259, causing conformant JSON parsers to reject the output. Affected versions include 2.13.1 through 2.25.4, 2.26.0, and 3.0.0-alpha1 through 3.0.0-beta2. The vulnerability affects applications using JsonTemplateLayout’s message resolver or another layout relying on MapMessage.asJson() or MapMessage.getFormattedMessage(new String[]{"JSON"}). Logging an attacker-controlled non-finite floating-point value can corrupt the enclosing log record or disrupt downstream ingestion and parsing. The earlier fix for CVE-2026-34481 did not cover all affected code paths.
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Apache Log4j API incorrectly serializes NaN, Infinity, and -Infinity as bare JSON tokens. Exploitation requires an application to log an attacker-controlled floating-point value in a MapMessage using JsonTemplateLayout's message resolver or another layout relying on MapMessage JSON serialization. Malformed output can corrupt log records or disrupt downstream ingestion and parsing. Fixed versions are 2.25.5 and 2.26.1; version 2.26.0 remains affected. The reference rates the vulnerability Medium, with CVSS v3 5.9 and CVSS v4 6.3.
A vulnerability in Oracle Enterprise Manager Cloud Control addressed by the September 15, 2026 patch release; no further technical details are provided.
Apache Log4j API JSON-serialization flaw: attacker-controlled NaN or infinity values in a MapMessage can yield malformed JSON, corrupt log records, or cause log-parser/ingestion disruption.
A vulnerability tracked as CVE-2026-49844 affecting Amazon Linux 2023 packages log4j-jcl and log4j-slf4j. It is rated CVSS v3 5.9 (network accessible, high attack complexity, no privileges or user interaction required, integrity impact) and CVSS v4 indicates low subsequent-system integrity impact.
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Cross-references every affected SKU, including bundled OEM variants.
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