CVE-2026-23352

  1. OpenCVE
  2. Vulnerabilities (CVE)
  3. CVE-2026-23352
In the Linux kernel, the following vulnerability has been resolved: x86/efi: defer freeing of boot services memory efi_free_boot_services() frees memory occupied by EFI_BOOT_SERVICES_CODE and EFI_BOOT_SERVICES_DATA using memblock_free_late(). There are two issue with that: memblock_free_late() should be used for memory allocated with memblock_alloc() while the memory reserved with memblock_reserve() should be freed with free_reserved_area(). More acutely, with CONFIG_DEFERRED_STRUCT_PAGE_INIT=y efi_free_boot_services() is called before deferred initialization of the memory map is complete. Benjamin Herrenschmidt reports that this causes a leak of ~140MB of RAM on EC2 t3a.nano instances which only have 512MB or RAM. If the freed memory resides in the areas that memory map for them is still uninitialized, they won't be actually freed because memblock_free_late() calls memblock_free_pages() and the latter skips uninitialized pages. Using free_reserved_area() at this point is also problematic because __free_page() accesses the buddy of the freed page and that again might end up in uninitialized part of the memory map. Delaying the entire efi_free_boot_services() could be problematic because in addition to freeing boot services memory it updates efi.memmap without any synchronization and that's undesirable late in boot when there is concurrency. More robust approach is to only defer freeing of the EFI boot services memory. Split efi_free_boot_services() in two. First efi_unmap_boot_services() collects ranges that should be freed into an array then efi_free_boot_services() later frees them after deferred init is complete.

5.5 /10

CVSS v3 : MEDIUM

V3 Legend

Vector :

Exploitability : 1.8 / Impact : 3.6

Attack Vector LOCAL

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References
Link Resource
https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d Patch
https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c Patch
https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6 Patch
https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64 Patch
https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d Patch
https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264 Patch
https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326 Patch
https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980 Patch
https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad Patch
Configurations

Configuration 1 (hide)

OR cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:2.6.39.1:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:3.0:-:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*
History

24 Apr 2026, 17:59

Type Values Removed Values Added
CPE cpe:2.3:o:linux:linux_kernel:3.0:-:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:2.6.39.1:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*
CVSS v2 : unknown
v3 : unknown 		v2 : unknown
v3 : 5.5
First Time Linux
Linux linux Kernel
CWE CWE-401
References () https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d - () https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d - Patch
References () https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c - () https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c - Patch
References () https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6 - () https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6 - Patch
References () https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64 - () https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64 - Patch
References () https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d - () https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d - Patch
References () https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264 - () https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264 - Patch
References () https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326 - () https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326 - Patch
References () https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980 - () https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980 - Patch
References () https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad - () https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad - Patch

18 Apr 2026, 09:16

Type Values Removed Values Added
References
  • () https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d -
  • () https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264 -
Summary
  • (es) En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta: x86/efi: aplazar la liberación de la memoria de servicios de arranque efi_free_boot_services() libera la memoria ocupada por EFI_BOOT_SERVICES_CODE y EFI_BOOT_SERVICES_DATA usando memblock_free_late(). Hay dos problemas con eso: memblock_free_late() debería usarse para la memoria asignada con memblock_alloc() mientras que la memoria reservada con memblock_reserve() debería liberarse con free_reserved_area(). Más agudamente, con CONFIG_DEFERRED_STRUCT_PAGE_INIT=y efi_free_boot_services() se llama antes de que se complete la inicialización diferida del mapa de memoria. Benjamin Herrenschmidt informa que esto causa una fuga de ~140MB de RAM en instancias EC2 t3a.nano que solo tienen 512MB de RAM. Si la memoria liberada reside en las áreas cuyo mapa de memoria aún no está inicializado, no se liberarán realmente porque memblock_free_late() llama a memblock_free_pages() y esta última omite las páginas no inicializadas. Usar free_reserved_area() en este punto también es problemático porque __free_page() accede al 'buddy' de la página liberada y eso de nuevo podría terminar en una parte no inicializada del mapa de memoria. Retrasar todo efi_free_boot_services() podría ser problemático porque además de liberar la memoria de servicios de arranque, actualiza efi.memmap sin ninguna sincronización y eso es indeseable tarde en el arranque cuando hay concurrencia. Un enfoque más robusto es aplazar solo la liberación de la memoria de servicios de arranque EFI. Dividir efi_free_boot_services() en dos. Primero, efi_unmap_boot_services() recopila los rangos que deberían liberarse en un array, luego efi_free_boot_services() los libera más tarde una vez que la inicialización diferida está completa.

25 Mar 2026, 11:16

Type Values Removed Values Added
New CVE
Information

Published : 2026-03-25 11:16

Updated : 2026-04-24 17:59

NVD link : CVE-2026-23352

Mitre link : CVE-2026-23352

CVE.ORG link : CVE-2026-23352

JSON object : View

Products Affected

linux

  • linux_kernel
CWE
CWE-401

Missing Release of Memory after Effective Lifetime