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CVE-2024-50115

Estado: ModificadaAlta (7.1)—

In the Linux kernel, the following vulnerability has been resolved:

KVM: nSVM: Ignore nCR3[4:0] when loading PDPTEs from memory

Ignore nCR3[4:0] when loading PDPTEs from memory for nested SVM, as bits 4:0 of CR3 are ignored when PAE paging is used, and thus VMRUN doesn't enforce 32-byte alignment of nCR3.

In the absolute worst case scenario, failure to ignore bits 4:0 can result in an out-of-bounds read, e.g. if the target page is at the end of a memslot, and the VMM isn't using guard pages.

Per the APM:

And the SDM's much more explicit:

Note, KVM gets this right when loading PDPTRs, it's only the nSVM flow that is broken.

Detalles técnicos trazas, registros y código del informe original
  The CR3 register points to the base address of the page-directory-pointer
  table. The page-directory-pointer table is aligned on a 32-byte boundary,
  with the low 5 address bits 4:0 assumed to be 0.

  4:0    Ignored

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Acceso local (AV:L) sin interacción del usuario permite escalada de privilegios en kernel KVM/nSVM. La lectura fuera de límites (out-of-bounds read) en PDPTEs permite acceso a datos del kernel.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Threat Intelligence ProgramExecution PreventionApplication Isolation and SandboxingExploit ProtectionUpdate SoftwareData Loss Prevention

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

Mostrar
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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: nSVM: Ignore nCR3[4:0] when loading PDPTEs from memory\n\nIgnore nCR3[4:0] when loading PDPTEs from memory for nested SVM, as bits\n4:0 of CR3 are ignored when PAE paging is used, and thus VMRUN doesn't\nenforce 32-byte alignment of nCR3.\n\nIn the absolute worst case scenario, failure to ignore bits 4:0 can result\nin an out-of-bounds read, e.g. if the target page is at the end of a\nmemslot, and the VMM isn't using guard pages.\n\nPer the APM:\n\n  The CR3 register points to the base address of the page-directory-pointer\n  table. The page-directory-pointer table is aligned on a 32-byte boundary,\n  with the low 5 address bits 4:0 assumed to be 0.\n\nAnd the SDM's much more explicit:\n\n  4:0    Ignored\n\nNote, KVM gets this right when loading PDPTRs, it's only the nSVM flow\nthat is broken."
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      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: KVM: nSVM: Ignorar nCR3[4:0] al cargar PDPTE desde la memoria Ignorar nCR3[4:0] al cargar PDPTE desde la memoria para SVM anidado, ya que los bits 4:0 de CR3 se ignoran cuando se utiliza la paginación PAE y, por lo tanto, VMRUN no aplica la alineación de 32 bytes de nCR3. En el peor de los casos, no ignorar los bits 4:0 puede dar como resultado una lectura fuera de los límites, por ejemplo, si la página de destino está al final de un memslot y el VMM no está utilizando páginas de protección. Según el APM: El registro CR3 apunta a la dirección base de la tabla de punteros de directorio de páginas. La tabla de punteros de directorio de página está alineada en un límite de 32 bytes, y se supone que los 5 bits de dirección bajos 4:0 son 0. Y el SDM es mucho más explícito: 4:0 Ignorado. Tenga en cuenta que KVM hace esto correctamente al cargar PDPTR, es solo el flujo nSVM el que está dañado."
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