CVE-2026-40023

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Conforming XML parsers must reject such documents with a fatal error, which may cause downstream log processing systems to drop or fail to index affected records.\n\nAn attacker who can influence logged data can exploit this to suppress individual log records, impairing audit trails and detection of malicious activity.\n\nUsers are advised to upgrade to Apache Log4cxx 1.7.0, which fixes this issue."}, {"lang": "es", "value": "El XMLLayout de Apache Log4cxx https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html , en versiones anteriores a la 1.7.0, no logra sanear los caracteres prohibidos por la especificaci\u00f3n XML 1.0 https://www.w3.org/TR/xml/#charsets en los mensajes de registro, y en las claves y valores de las propiedades NDC y MDC, produciendo una salida XML no v\u00e1lida. Los analizadores XML conformes deben rechazar dichos documentos con un error fatal, lo que puede provocar que los sistemas de procesamiento de registros posteriores descarten o no indexen los registros afectados.\n\nUn atacante que puede influir en los datos registrados puede explotar esto para suprimir registros de log individuales, lo que perjudica las pistas de auditor\u00eda y la detecci\u00f3n de actividad maliciosa.\n\nSe aconseja a los usuarios actualizar a Apache Log4cxx 1.7.0, que corrige este problema."}], "id": "CVE-2026-40023", "lastModified": "2026-10-26T21:10:00.170", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "HIGH", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.3, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "LOW", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "security@apache.org", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-40023", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-10T17:28:20.094265Z", "version": "2.0.3"}}]}, "published": "2026-04-10T16:16:32.600", "references": [{"source": "security@apache.org", "tags": ["Issue Tracking", "Patch"], "url": "https://github.com/apache/logging-log4cxx/pull/609"}, {"source": "security@apache.org", "tags": ["Mailing List", "Vendor Advisory"], "url": "https://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b"}, {"source": "security@apache.org", "tags": ["Product"], "url": "https://logging.apache.org/cyclonedx/vdr.xml"}, {"source": "security@apache.org", "tags": ["Product"], "url": "https://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html"}, {"source": "security@apache.org", "tags": ["Vendor Advisory"], "url": "https://logging.apache.org/security.html#CVE-2026-40023"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "http://www.openwall.com/lists/oss-security/2026/04/10/12"}], "sourceIdentifier": "security@apache.org", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-116"}], "source": "security@apache.org", "type": "Secondary"}]}

{"bugzilla": {"description": "Apache Log4cxx: Apache Log4cxx: Log processing impairment due to unsanitized XML characters", "id": "2457317", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2457317"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "status": "draft"}, "cwe": "CWE-117", "details": ["A flaw was found in Apache Log4cxx. An attacker who can influence logged data can exploit this by injecting characters forbidden by the XML 1.0 specification (a standard for encoding documents) into log messages, Network Device Configuration (NDC), and Mapped Diagnostic Context (MDC) property keys and values. This results in invalid XML output, causing downstream log processing systems to drop or fail to index affected records. The primary impact is the impairment of audit trails and the detection of malicious activity, leading to a Denial of Service (DoS) for log processing."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2026-40023", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "log4cxx", "product_name": "Red Hat Enterprise Linux 7"}], "public_date": "2026-04-10T15:45:52Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-40023\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-40023\nhttps://github.com/apache/logging-log4cxx/pull/609\nhttps://lists.apache.org/thread/y15cv3zblg3dfwr5vy6ddbnl4zyrzr8b\nhttps://logging.apache.org/cyclonedx/vdr.xml\nhttps://logging.apache.org/log4cxx/1.7.0/classlog4cxx_1_1xml_1_1XMLLayout.html\nhttps://logging.apache.org/security.html#CVE-2026-40023"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,1.7.0)"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Apache Log4cxx", "source": "cna", "vendor": "Apache Software Foundation"}, "product": "log4cxx", "vendor": "apache"}], "analysis": {"en": {"generated_at": "2026-04-14T01:40:10.206572+00:00", "value": {"mitigation_remediation": ["Upgrade Apache Log4cxx to version 1.7.0 or later to eliminate XML layout sanitization issues."], "summary": {"action": "Immediate patch", "impact": "Log event suppression and audit trail impairment"}, "threat_synthesis": {"affected_systems": "Affects Apache Log4cxx, the Brew distribution of Log4cxx and the Conan package of Log4cxx when used in any version earlier than 1.7.0. Users of these libraries should verify the version in use and consider upgrading.", "description_and_impact": "Apache Log4cxx\u2019s XMLLayout fails to escape XML 1.0 forbidden characters in logged data, charting, NDC and MDC keys and values in versions prior to 1.7.0. The resulting invalid XML documents are rejected by conforming parsers, causing log entries to be silently dropped or processed systems to fail to index them. An attacker who can inject or influence logged messages can use this flaw to erase evidence of activity, degrading audit trails and hindering detection of malicious actions.", "risk_and_exploitability": "The vulnerability carries a CVSS score of 6.3, indicating medium severity, and an EPSS score below 1\u202f%, suggesting a low probability of widespread exploitation. It is not listed in the CISA Known Exploited Vulnerabilities catalog. Exploitation requires an attacker\u2019s ability to supply log data that the application records, a condition that may arise from local code execution or from remote inputs that are directly logged. The likely attack vector is via application input that ends up in log messages or contextual data libraries."}}}}, "created": "2026-04-13T12:44:38.041996+00:00", "updated": "2026-04-14T16:36:22.537878+00:00", "vendors": ["apache", "apache$PRODUCT$log4cxx"]}