CVE-2026-23352x86/efi: defer freeing of boot services memory
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 0aed459e8487eb6ebdb4efe8cefe1eafbc704b30 before 4a2cb90c538f06c873a187aa743575d48685d7a6; from 916f676f8dc016103f983c7ec54c18ecdbb6e349 before 7131bd1fecc749bc94fb44aae217bbd8a8a85264; 916f676f8dc016103f983c7ec54c18ecdbb6e349 builds before 6d8ba221e7aafaa2f284b7d22faee814c28e009d; from 916f676f8dc016103f983c7ec54c18ecdbb6e349 before 227688312fece0026fc67a00ba9a0b3611ebe95d; 916f676f8dc016103f983c7ec54c18ecdbb6e349 builds before 6a25e25279282c5c8ade554c04c6ab9dc7902c64; 916f676f8dc016103f983c7ec54c18ecdbb6e349 builds before 399da820ecfe6f4f10c143e5c453d3559a04db9c; from 916f676f8dc016103f983c7ec54c18ecdbb6e349 before f9e9cc320854a76a39e7bc92d144554f3a727fad; 916f676f8dc016103f983c7ec54c18ecdbb6e349 builds before 7dcf59422a3b0d20ddda844f856b4a1e0608a326; and 2 more ranges | CNA record |
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem siemens:simatic_s7_1500_tm_mfp_gnu_linux_subsystem (from the name) | all versions | CISA ADP |
linux linux_kernel linux:linux_kernel | from 3.0.1 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.167; from 6.2 before 6.6.130; from 6.7 before 6.12.77; from 6.13 before 6.18.17; from 6.19 before 6.19.7; 2.6.39.1; and 8 more ranges | NVD |
References
- https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6patch
- https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264patch
- https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009dpatch
- https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95dpatch
- https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64patch
- https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9cpatch
- https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fadpatch
- https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326patch
- https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980patch
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.