CVE-2026-21452

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{"affected": [{"affectedData": [{"product": "msgpack-java", "vendor": "msgpack", "versions": [{"status": "affected", "version": "< 0.9.11"}]}], "source": "security-advisories@github.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:msgpack:messagepack:0.9.10:*:*:*:*:java:*:*", "matchCriteriaId": "F2E0553D-FF80-4F6B-935E-8C97E16894DC", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "MessagePack for Java is a serializer implementation for Java. A denial-of-service vulnerability exists in versions prior to 0.9.11 when deserializing .msgpack files containing EXT32 objects with attacker-controlled payload lengths. While MessagePack-Java parses extension headers lazily, it later trusts the declared EXT payload length when materializing the extension data. When ExtensionValue.getData() is invoked, the library attempts to allocate a byte array of the declared length without enforcing any upper bound. A malicious .msgpack file of only a few bytes can therefore trigger unbounded heap allocation, resulting in JVM heap exhaustion, process termination, or service unavailability. This vulnerability is triggered during model loading / deserialization, making it a model format vulnerability suitable for remote exploitation. The vulnerability enables a remote denial-of-service attack against applications that deserialize untrusted .msgpack model files using MessagePack for Java. A specially crafted but syntactically valid .msgpack file containing an EXT32 object with an attacker-controlled, excessively large payload length can trigger unbounded memory allocation during deserialization. When the model file is loaded, the library trusts the declared length metadata and attempts to allocate a byte array of that size, leading to rapid heap exhaustion, excessive garbage collection, or immediate JVM termination with an OutOfMemoryError. The attack requires no malformed bytes, user interaction, or elevated privileges and can be exploited remotely in real-world environments such as model registries, inference services, CI/CD pipelines, and cloud-based model hosting platforms that accept or fetch .msgpack artifacts. Because the malicious file is extremely small yet valid, it can bypass basic validation and scanning mechanisms, resulting in complete service unavailability and potential cascading failures in production systems. Version 0.9.11 fixes the vulnerability."}, {"lang": "es", "value": "MessagePack para Java es una implementaci\u00f3n de serializador para Java. Una vulnerabilidad de denegaci\u00f3n de servicio existe en versiones anteriores a la 0.9.11 al deserializar archivos .msgpack que contienen objetos EXT32 con longitudes de carga \u00fatil controladas por el atacante. Aunque MessagePack-Java analiza los encabezados de extensi\u00f3n de forma perezosa, luego conf\u00eda en la longitud de carga \u00fatil EXT declarada al materializar los datos de la extensi\u00f3n. Cuando se invoca ExtensionValue.getData(), la biblioteca intenta asignar una matriz de bytes de la longitud declarada sin imponer ning\u00fan l\u00edmite superior. Un archivo .msgpack malicioso de solo unos pocos bytes puede, por lo tanto, desencadenar una asignaci\u00f3n de pila ilimitada, lo que resulta en el agotamiento de la pila de la JVM, la terminaci\u00f3n del proceso o la indisponibilidad del servicio. Esta vulnerabilidad se desencadena durante la carga / deserializaci\u00f3n del modelo, lo que la convierte en una vulnerabilidad de formato de modelo adecuada para la explotaci\u00f3n remota. La vulnerabilidad permite un ataque remoto de denegaci\u00f3n de servicio contra aplicaciones que deserializan archivos de modelo .msgpack no confiables utilizando MessagePack para Java. Un archivo .msgpack especialmente dise\u00f1ado pero sint\u00e1cticamente v\u00e1lido que contiene un objeto EXT32 con una longitud de carga \u00fatil excesivamente grande y controlada por el atacante puede desencadenar una asignaci\u00f3n de memoria ilimitada durante la deserializaci\u00f3n. Cuando se carga el archivo del modelo, la biblioteca conf\u00eda en los metadatos de longitud declarada e intenta asignar una matriz de bytes de ese tama\u00f1o, lo que lleva a un r\u00e1pido agotamiento de la pila, una recolecci\u00f3n de basura excesiva o la terminaci\u00f3n inmediata de la JVM con un OutOfMemoryError. El ataque no requiere bytes malformados, interacci\u00f3n del usuario o privilegios elevados y puede explotarse de forma remota en entornos del mundo real como registros de modelos, servicios de inferencia, pipelines de CI/CD y plataformas de alojamiento de modelos basadas en la nube que aceptan o recuperan artefactos .msgpack. Debido a que el archivo malicioso es extremadamente peque\u00f1o pero v\u00e1lido, puede eludir los mecanismos b\u00e1sicos de validaci\u00f3n y escaneo, lo que resulta en una indisponibilidad completa del servicio y posibles fallas en cascada en los sistemas de producci\u00f3n. La versi\u00f3n 0.9.11 corrige la vulnerabilidad."}], "id": "CVE-2026-21452", "lastModified": "2026-06-17T10:18:41.907", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-21452", "options": [{"exploitation": "poc"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-01-02T21:21:49.839128Z", "version": "2.0.3"}}]}, "published": "2026-01-02T21:16:03.067", "references": [{"source": "security-advisories@github.com", "tags": ["Patch"], "url": "https://github.com/msgpack/msgpack-java/commit/daa2ea6b2f11f500e22c70a22f689f7a9debdeae"}, {"source": "security-advisories@github.com", "tags": ["Release Notes"], "url": "https://github.com/msgpack/msgpack-java/releases/tag/v0.9.11"}, {"source": "security-advisories@github.com", "tags": ["Exploit", "Third Party Advisory"], "url": "https://github.com/msgpack/msgpack-java/security/advisories/GHSA-cw39-r4h6-8j3x"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-400"}, {"lang": "en", "value": "CWE-789"}], "source": "security-advisories@github.com", "type": "Secondary"}, {"description": [{"lang": "en", "value": "NVD-CWE-Other"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{}

{"analysis": {"en": {"generated_at": "2026-04-18T08:28:12.735211+00:00", "value": {"mitigation_remediation": ["Upgrade MessagePack\u2011Java to version 0.9.11 or later.", "Validate all incoming .msgpack files before deserialization; enforce strict length checks or use a whitelist of trusted sources.", "Configure JVM memory limits and monitor heap usage to detect sudden expansion; consider sandboxing the deserialization process with restricted resources."], "summary": {"action": "Apply Patch", "impact": "Remote Denial of Service"}, "threat_synthesis": {"affected_systems": "Vulnerable packages are msgpack:msgpack-java 0.9.10 and earlier. The affected components are the MessagePack\u2011Java serializer used during model loading, for example in machine\u2011learning inference services, model registries, CI/CD pipelines, and cloud\u2011based hosting platforms that consume .msgpack artifacts. The vulnerability exists in the core extension handling code of the library, specifically the ExtensionValue.getData() method after the lazy header parse.", "description_and_impact": "MessagePack for Java deserializes .msgpack files and is vulnerable to a denial\u2011of\u2011service in versions before 0.9.11. An attacker can supply a valid EXT32 object whose declared payload length far exceeds the file size. The library lazily parses the header but later trusts that length when allocating a byte array. Because no upper bound is enforced, a small malicious file can force the library to allocate an enormous buffer, exhausting the JVM heap, triggering frequent garbage collection, or causing the process to terminate with an OutOfMemoryError.", "risk_and_exploitability": "CVSS base score is 7.5 with no malicious payload required beyond a syntactically valid .msgpack file, making exploitation trivial once an untrusted file can be processed. EPSS is less than 1\u202f%, suggesting the vulnerability has not yet been widely exploited, and it is not catalogued in KEV. Because the attack occurs during deserialization, any application that imports or loads model files without validating the source is exposed. The risk is high for services that expose a file\u2011upload interface or fetch artifacts from external repositories; once triggered, the service becomes completely unavailable."}}}}, "created": "2026-01-05T10:13:47.630593+00:00", "updated": "2026-04-18T08:30:35.834452+00:00", "vendors": ["msgpack", "msgpack$PRODUCT$msgpack"]}