CVE-2026-34481 (GCVE-0-2026-34481)

Vulnerability from cvelistv5 – Published: 2026-04-10 15:43 – Updated: 2026-07-11 04:55
VLAI
Title
Apache Log4j JSON Template Layout: Improper serialization of non-finite floating-point values in JsonTemplateLayout
Summary
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.
Severity
6.3 (Medium)
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-116 - Improper Encoding or Escaping of Output
Assigner
References
Impacted products
Vendor Product Version
Apache Software Foundation Apache Log4j JSON Template Layout Affected: 2.14.0 , < 2.25.4 (maven)
Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta3 (maven)
    cpe:2.3:a:apache:log4j_layout_template_json:*:*:*:*:*:*:*:*
 Create a notification for this product.
Credits
Ap4sh (Samy Medjahed) and Ethicxz (Eliott Laurie)
Show details on NVD website
To clipboard 

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Karwasz\"}, {\"lang\": \"en\", \"time\": \"2026-03-24T23:06:00.000Z\", \"value\": \"Fix shared publicly by Piotr P. Karwasz as pull request #4080\"}, {\"lang\": \"en\", \"time\": \"2026-03-25T09:54:00.000Z\", \"value\": \"Fix verified by the reporter\"}, {\"lang\": \"en\", \"time\": \"2026-03-28T11:19:00.000Z\", \"value\": \"Log4j 2.25.4 released\"}], \"references\": [{\"url\": \"https://github.com/apache/logging-log4j2/pull/4080\", \"tags\": [\"patch\"]}, {\"url\": \"https://logging.apache.org/security.html#CVE-2026-34481\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://logging.apache.org/cyclonedx/vdr.xml\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://logging.apache.org/log4j/2.x/manual/json-template-layout.html\", \"tags\": [\"related\"]}, {\"url\": \"https://lists.apache.org/thread/n34zdv00gbkdbzt2rx9rf5mqz6lhopcv\", \"tags\": [\"vendor-advisory\"]}], \"x_generator\": {\"engine\": \"Vulnogram 0.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Apache Log4j\u0027s  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.\\n\\nAn attacker can exploit this issue only if both of the following conditions are met:\\n\\n  *  The application uses JsonTemplateLayout.\\n  *  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.\\n\\n\\nUsers are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue.\\n\\nNote: 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.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eApache Log4j\u0027s \u003ccode\u003e\u003ca target=\\\"_blank\\\" rel=\\\"nofollow\\\" href=\\\"https://logging.apache.org/log4j/2.x/manual/json-template-layout.html\\\"\u003eJsonTemplateLayout\u003c/a\u003e\u003c/code\u003e, in versions up to and including 2.25.3, produces invalid JSON output when log events contain non-finite floating-point values (\u003ccode\u003eNaN\u003c/code\u003e, \u003ccode\u003eInfinity\u003c/code\u003e, or \u003ccode\u003e-Infinity\u003c/code\u003e), which are prohibited by RFC 8259. This may cause downstream log processing systems to reject or fail to index affected records.\u003c/p\u003e\u003cp\u003eAn attacker can exploit this issue only if both of the following conditions are met:\u003c/p\u003e\u003cul\u003e\u003cli\u003eThe application uses \u003ccode\u003eJsonTemplateLayout\u003c/code\u003e.\u003c/li\u003e\u003cli\u003eThe application logs a \u003ccode\u003eMapMessage\u003c/code\u003e, or logs an object directly (e.g., via \u003ccode\u003eLogger.info(Object)\u003c/code\u003e, which wraps it in an \u003ccode\u003eObjectMessage\u003c/code\u003e), where the message contains an attacker-controlled floating-point value.\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eUsers are advised to upgrade to Apache Log4j JSON Template Layout 2.25.4, which corrects this issue.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eNote:\u003c/strong\u003e 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 \u003ccode\u003eMapMessage.asJson()\u003c/code\u003e serialization in Apache Log4j API and is fixed in versions 2.25.5 and 2.26.1.\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-116\", \"description\": \"CWE-116 Improper Encoding or Escaping of Output\"}]}], \"providerMetadata\": {\"orgId\": \"f0158376-9dc2-43b6-827c-5f631a4d8d09\", \"shortName\": \"apache\", \"dateUpdated\": \"2026-07-11T04:55:42.502Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-34481\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-11T04:55:42.502Z\", \"dateReserved\": \"2026-03-28T19:23:37.127Z\", \"assignerOrgId\": \"f0158376-9dc2-43b6-827c-5f631a4d8d09\", \"datePublished\": \"2026-04-10T15:43:00.100Z\", \"assignerShortName\": \"apache\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.