CVE-2026-23352

MEDIUM EPSS 2.6%
Published Mar 25, 20263mo ago · Modified Jun 17, 20262w ago
5.5 CVSS 3.1
Medium
Find Similar
Published Mar 25, 2026 3mo ago
Last Modified Jun 17, 2026 2w ago

Description

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.

CVSS Details

Base Score
5.5
Exploitability
1.8
Impact
3.6
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
2.6% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-401

Affected Products 16

VendorProductVersionRange
linuxlinux_kernel*≥3.0.1  –  <5.10.253
linuxlinux_kernel*≥5.11  –  <5.15.203
linuxlinux_kernel*≥5.16  –  <6.1.167
linuxlinux_kernel*≥6.2  –  <6.6.130
linuxlinux_kernel*≥6.7  –  <6.12.77
linuxlinux_kernel*≥6.13  –  <6.18.17
linuxlinux_kernel*≥6.19  –  <6.19.7
linuxlinux_kernel2.6.39.1any
linuxlinux_kernel3.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any
linuxlinux_kernel7.0any

References 9

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

Remediation

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