CVE-2026-23352x86/efi: defer freeing of boot services memory
- 5.5MediumCVSS base score
- 0.14%Exploitation in 30 daysEPSS · top 97% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By Linux
- 2 months later
· 2 months later
Published
- 8 months later
· 8 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.14% · top 97% of all CVEs (12 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Affected products
- affected 0aed459e8487eb6ebdb4efe8cefe1eafbc704b30 – < 4a2cb90c538f06c873a187aa743575d48685d7a6
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < 7131bd1fecc749bc94fb44aae217bbd8a8a85264
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < 6d8ba221e7aafaa2f284b7d22faee814c28e009d
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < 227688312fece0026fc67a00ba9a0b3611ebe95d
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < 6a25e25279282c5c8ade554c04c6ab9dc7902c64
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < 399da820ecfe6f4f10c143e5c453d3559a04db9c
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < f9e9cc320854a76a39e7bc92d144554f3a727fad
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < 7dcf59422a3b0d20ddda844f856b4a1e0608a326
- affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 – < a4b0bf6a40f3c107c67a24fbc614510ef5719980
- affected 2.6.39.1 – < 2.6.39.2
- affected 3.0
- unaffected < 3.0
- unaffected 2.6.39.2 – ≤ 2.6.*
- unaffected 5.10.253 – ≤ 5.10.*
- unaffected 5.15.203 – ≤ 5.15.*
- unaffected 6.1.167 – ≤ 6.1.*
- unaffected 6.6.130 – ≤ 6.6.*
- unaffected 6.12.77 – ≤ 6.12.*
- unaffected 6.18.17 – ≤ 6.18.*
- unaffected 6.19.7 – ≤ 6.19.*
- unaffected 7.0 – ≤ *
References
References10
- https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6 (opens in a new tab)
- https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264 (opens in a new tab)
- https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d (opens in a new tab)
- https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d (opens in a new tab)
- https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64 (opens in a new tab)
- https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c (opens in a new tab)
- https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad (opens in a new tab)
- https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326 (opens in a new tab)
- https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980 (opens in a new tab)
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-15325 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-23352)Record last updated .