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CVE-2026-23352· NVD / CVE Program· CNA Linux

x86/efi: defer freeing of boot services memory

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.13% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 2.6.39.2, 227688312fece0026fc67a00ba9a0b3611ebe95d, 399da820ecfe6f4f10c143e5c453d3559a04db9c; azl3 kernel 6.6.126.1-1 on Azure Linux 3.0 6.6.130.1-1; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes.

Low priority for now. Upgrade to Linux Linux 2.6.39.2, 227688312fece0026fc67a00ba9a0b3611ebe95d, 399da820ecfe6f4f10c143e5c453d3559a04db9c; azl3 kernel 6.6.126.1-1 on Azure Linux 3.0 6.6.130.1-1; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Mar 25, 2026
Updated
Oct 15, 2026
EPSS
0.1% · 2th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel3.0.1 and later · before 5.10.253
  • linux linux kernel5.11 and later · before 5.15.203
  • linux linux kernel5.16 and later · before 6.1.167
  • linux linux kernel6.2 and later · before 6.6.130
  • linux linux kernel6.7 and later · before 6.12.77
  • linux linux kernel6.13 and later · before 6.18.17
  • linux linux kernel6.19 and later · before 6.19.7
  • linux linux kernel2.6.39.1
  • linux linux kernel3.0
  • linux linux kernel7.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 3.0affected
    • 0aed459e8487eb6ebdb4efe8cefe1eafbc704b30 and later · before 4a2cb90c538f06c873a187aa743575d48685d7a6affected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before 7131bd1fecc749bc94fb44aae217bbd8a8a85264affected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before 6d8ba221e7aafaa2f284b7d22faee814c28e009daffected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before 227688312fece0026fc67a00ba9a0b3611ebe95daffected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before 6a25e25279282c5c8ade554c04c6ab9dc7902c64affected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before 399da820ecfe6f4f10c143e5c453d3559a04db9caffected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before f9e9cc320854a76a39e7bc92d144554f3a727fadaffected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before 7dcf59422a3b0d20ddda844f856b4a1e0608a326affected · git
    • 916f676f8dc016103f983c7ec54c18ecdbb6e349 and later · before a4b0bf6a40f3c107c67a24fbc614510ef5719980affected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.8-16.19.8-1
openSUSE:Leap 16.0dtb-aarch64before 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-64kbbefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-azurebefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-defaultbefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-default-basebefore 6.12.0-160000.39.1.160000.2.256.12.0-160000.39.1.160000.2.25
openSUSE:Leap 16.0kernel-docsbefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-kvmsmallbefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-obs-buildbefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-obs-qabefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-rtbefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-sourcebefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-symsbefore 6.12.0-160000.39.16.12.0-160000.39.1
openSUSE:Leap 16.0kernel-zfcpdumpbefore 6.12.0-160000.39.16.12.0-160000.39.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7_Update_22before 1-150700.15.3.11-150700.15.3.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7-RT_Update_21before 1-150700.1.3.11-150700.1.3.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-64kbbefore 6.4.0-150700.53.84.16.4.0-150700.53.84.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-defaultbefore 6.4.0-150700.53.84.16.4.0-150700.53.84.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-default-basebefore 6.4.0-150700.53.84.1.150700.17.47.16.4.0-150700.53.84.1.150700.17.47.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-sourcebefore 6.4.0-150700.53.84.16.4.0-150700.53.84.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7kernel-zfcpdumpbefore 6.4.0-150700.53.84.16.4.0-150700.53.84.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7kernel-docsbefore 6.4.0-150700.53.84.16.4.0-150700.53.84.1

+25

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now
  • CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV
    83Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-23343Mar 25, 2026 · xdp: produce a warning when calculated tailroom is negative
    31Monitor
  • ← EarlierCVE-2026-23351Mar 25, 2026 · netfilter: nft_set_pipapo: split gc into unlink and reclaim phase
    31Monitor
  • Later →CVE-2026-23356Mar 25, 2026 · drbd: fix "LOGIC BUG" in drbd_al_begin_io_nonblock()
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux2.6.39.2Vendor (CNA)
Linux Linux227688312fece0026fc67a00ba9a0b3611ebe95dVendor (CNA)
Linux Linux399da820ecfe6f4f10c143e5c453d3559a04db9cVendor (CNA)
Linux Linux4a2cb90c538f06c873a187aa743575d48685d7a6Vendor (CNA)
Linux Linux6a25e25279282c5c8ade554c04c6ab9dc7902c64Vendor (CNA)
Linux Linux6d8ba221e7aafaa2f284b7d22faee814c28e009dVendor (CNA)
Linux Linux7131bd1fecc749bc94fb44aae217bbd8a8a85264Vendor (CNA)
Linux Linux7dcf59422a3b0d20ddda844f856b4a1e0608a326Vendor (CNA)
Linux Linuxa4b0bf6a40f3c107c67a24fbc614510ef5719980Vendor (CNA)
Linux Linuxf9e9cc320854a76a39e7bc92d144554f3a727fadVendor (CNA)
azl3 kernel 6.6.126.1-1 on Azure Linux 3.06.6.130.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0Release NotesMicrosoft (MSRC)
debian:linux6.1.170-1 · Debian:12Package registry (OSV)
opensuse:dtb-aarch646.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-64kb6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-azure6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-default-base6.12.0-160000.39.1.160000.2.25 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-docs6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-kvmsmall6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-build6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-obs-qa6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-rt6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-source6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
opensuse:kernel-syms6.12.0-160000.39.1 · openSUSE:Leap 16.0Package registry (OSV)
suse:kernel-64kb6.12.0-160000.39.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-64kb6.4.0-150700.53.84.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP7Package registry (OSV)
suse:kernel-azure6.12.0-160000.39.1 · SUSE:Linux Enterprise Server 16.0Package registry (OSV)
suse:kernel-default6.4.0-150700.53.84.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP7Package registry (OSV)
suse:kernel-default6.4.0-159998.53.1 · SUSE:Linux Micro 6.1Package registry (OSV)

+19

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-401 · Missing Release of Memory after Effective Lifetime

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (9 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records