Vulnerability-Lookup

(CVE-2026-49844)

Vulnerability from cleanstart – Published: 2026-10-01 00:35 – Updated: 2026-10-08 15:57 – Source website

Summary

Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON

Details

CVE-2026-49844 affects multiple packages. Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON. See references for individual vulnerability details.

Severity

5.9 (Medium)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

References

URL

Type

	https://github.com/cleanstart-dev/cleanstart-secu…	ADVISORY
	https://osv.dev/vulnerability/CVE-2026-49844	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-49844	WEB

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "CleanStart",
        "name": "elasticsearch",
        "purl": "pkg:apk/cleanstart/elasticsearch"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.3.8-r6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "CleanStart",
        "name": "apache-nifi",
        "purl": "pkg:apk/cleanstart/apache-nifi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.5.0-r1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "credits": [],
  "database_specific": {},
  "details": "CVE-2026-49844 affects multiple packages. Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON. See references for individual vulnerability details.",
  "id": "CLEANSTART-2026-KK56976",
  "modified": "2026-10-08T15:57:40Z",
  "published": "2026-10-01T00:35:38.593187Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/cleanstart-dev/cleanstart-security-advisories/tree/main/advisories/2026/CLEANSTART-2026-KK56976.json"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-49844"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-49844"
    }
  ],
  "related": [],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON",
  "upstream": [
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  ]
}

CVE-2026-49844 (GCVE-0-2026-49844)

Vulnerability from cvelistv5 – Published: 2026-07-10 21:14 – Updated: 2026-09-17 18:37

Title

Apache Log4j API: Improper serialization of non-finite floating-point values in MapMessage.asJson()

Summary

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.

Severity

6.3 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/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 · CISA-ADP (v2.0.3)

Decision recorded 2026-07-14 13:56 UTC

CWE

CWE-116 - Improper Encoding or Escaping of Output

Assigner

apache CNA under the mitre root

CNA scorecard B 76/100 over 936 records in the last 180 days details

References

4 references

URL	Tags
https://logging.apache.org/log4j/2.x/manual/json-…	related
https://github.com/apache/logging-log4j2/pull/4163	patch
https://logging.apache.org/cyclonedx/vdr.xml	vendor-advisory
https://logging.apache.org/security.html#CVE-2026-49844	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
Apache Software Foundation	Apache Log4j API	Affected: 2.13.1 , < 2.25.5 (maven) Affected: 2.26.0 , < 2.26.1 (maven) Affected: 3.0.0-alpha1 , ≤ 3.0.0-beta2 (maven) cpe:2.3:a:apache:log4j_api::::::::

Credits

Himanshu Anand

Show details on NVD website

JSON

To clipboard

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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.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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