CVE-2026-23352 (GCVE-0-2026-23352)
Vulnerability from cvelistv5 – Published: 2026-03-25 10:27 – Updated: 2026-11-05 21:33
VLAI
EPSS
VEX
Title
x86/efi: defer freeing of boot services memory
Summary
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.
Severity
No CVSS data available.
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-11-05 21:27 UTC
Assigner
References
10 references
Impacted products
3 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
0aed459e8487eb6ebdb4efe8cefe1eafbc704b30 , < 4a2cb90c538f06c873a187aa743575d48685d7a6
(git)
Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < 7131bd1fecc749bc94fb44aae217bbd8a8a85264 (git) Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < 6d8ba221e7aafaa2f284b7d22faee814c28e009d (git) Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < 227688312fece0026fc67a00ba9a0b3611ebe95d (git) Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < 6a25e25279282c5c8ade554c04c6ab9dc7902c64 (git) Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < 399da820ecfe6f4f10c143e5c453d3559a04db9c (git) Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < f9e9cc320854a76a39e7bc92d144554f3a727fad (git) Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < 7dcf59422a3b0d20ddda844f856b4a1e0608a326 (git) Affected: 916f676f8dc016103f983c7ec54c18ecdbb6e349 , < a4b0bf6a40f3c107c67a24fbc614510ef5719980 (git) Affected: 2.6.39.1 , < 2.6.39.2 (semver) |
guessed | |
| Linux | Linux |
Affected:
3.0
Unaffected: 0 , < 3.0 (semver) Unaffected: 2.6.39.2 , ≤ 2.6.* (semver) Unaffected: 5.10.253 , ≤ 5.10.* (semver) Unaffected: 5.15.203 , ≤ 5.15.* (semver) Unaffected: 6.1.167 , ≤ 6.1.* (semver) Unaffected: 6.6.130 , ≤ 6.6.* (semver) Unaffected: 6.12.77 , ≤ 6.12.* (semver) Unaffected: 6.18.17 , ≤ 6.18.* (semver) Unaffected: 6.19.7 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix) |
guessed | |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem |
Affected:
0 , < *
(custom)
|
guessed |
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},
{
"url": "https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326"
},
{
"url": "https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980"
}
],
"title": "x86/efi: defer freeing of boot services memory",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-23352",
"datePublished": "2026-03-25T10:27:37.500Z",
"dateReserved": "2026-01-13T15:37:46.000Z",
"dateUpdated": "2026-11-05T21:33:41.778Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.