CVE-2026-93253
In the Linux kernel, the following vulnerability has been resolved:
sched/isolation: Defer freeing of cpumask memblock memory to initcall
When testing a linux-next kernel with commit 59bd1d914bb5 ("memblock: warn when freeing reserved memory before memory map is initialized"), the following warning was hit when there was a "nohz_full" kernel boot parameter.
IOW, we shouldn't free memblock allocated memory so early in the boot process when memory map isn't fully initialized in deferred_init_memmap().
Fix it by saving the housekeeping cpumask memblock memory to be freed into a llist free list in housekeeping_init() and add a new housekeeping_late_init() helper to defer the actual freeing of memblock memory to when initcall's are being processed.
Read full descriptionShow less
The cpumask memblock memory is treated as a llist_node with the size of a "long" type which is also smallest cpumask size that can be allocated.
The non-atomic version of the llist APIs are used as there is no contention.
This commit depends on the presence of commit 7c2eee9c1367 ("memblock: don't touch memblock arrays when memblock_free() is called late") to prevent a KASAN UAF bug report [1].
[1] https://lore.kernel.org/lkml/20260505051821.1107133-1-longman@redhat.com/
Technical details traces, logs and code from the original report
Cannot free reserved memory because of deferred initialization of the memory map
WARNING: mm/memblock.c:904 at __free_reserved_area+0xde/0xf0, CPU#0: swapper/0/0
:
Call Trace:
<TASK>
memblock_phys_free+0xcb/0x100
housekeeping_init+0x14c/0x170
start_kernel+0x207/0x450
x86_64_start_reservations+0x24/0x30
x86_64_start_kernel+0xda/0xe0
common_startup_64+0x13e/0x141
</TASK>CVSS
NVD hasn't assigned a CVSS score to this CVE (common since the April 2026 policy change).
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 0.19%
- Percentile among all scored CVEs: 8
- Score date: 10/5/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.
References
Raw JSON (NVD)
Show
{
"id": "CVE-2026-93253",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "27c3a5967f054ab666704cb28f2aeb18ca07cab7",
"lessThan": "811fdac2d1bdf0b0d3fda262aac288ddd13a1422",
"versionType": "git"
},
{
"status": "affected",
"version": "27c3a5967f054ab666704cb28f2aeb18ca07cab7",
"lessThan": "2b58c749b8c5244e259a0230bc57b10b010dc545",
"versionType": "git"
}
],
"programFiles": [
"kernel/sched/isolation.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "7.2.6",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/sched/isolation.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-24T16:17:21.640",
"references": [
{
"url": "https://git.kernel.org/stable/c/2b58c749b8c5244e259a0230bc57b10b010dc545",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/811fdac2d1bdf0b0d3fda262aac288ddd13a1422",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/isolation: Defer freeing of cpumask memblock memory to initcall\n\nWhen testing a linux-next kernel with commit 59bd1d914bb5 (\"memblock:\nwarn when freeing reserved memory before memory map is initialized\"),\nthe following warning was hit when there was a \"nohz_full\" kernel boot\nparameter.\n\n Cannot free reserved memory because of deferred initialization of the memory map\n WARNING: mm/memblock.c:904 at __free_reserved_area+0xde/0xf0, CPU#0: swapper/0/0\n :\n Call Trace:\n <TASK>\n memblock_phys_free+0xcb/0x100\n housekeeping_init+0x14c/0x170\n start_kernel+0x207/0x450\n x86_64_start_reservations+0x24/0x30\n x86_64_start_kernel+0xda/0xe0\n common_startup_64+0x13e/0x141\n </TASK>\n\nIOW, we shouldn't free memblock allocated memory so early\nin the boot process when memory map isn't fully initialized in\ndeferred_init_memmap().\n\nFix it by saving the housekeeping cpumask memblock memory to be\nfreed into a llist free list in housekeeping_init() and add a new\nhousekeeping_late_init() helper to defer the actual freeing of memblock\nmemory to when initcall's are being processed. The cpumask memblock\nmemory is treated as a llist_node with the size of a \"long\" type which\nis also smallest cpumask size that can be allocated.\n\nThe non-atomic version of the llist APIs are used as there is no\ncontention.\n\nThis commit depends on the presence of commit 7c2eee9c1367 (\"memblock:\ndon't touch memblock arrays when memblock_free() is called late\")\nto prevent a KASAN UAF bug report [1].\n\n [1] https://lore.kernel.org/lkml/20260505051821.1107133-1-longman@redhat.com/"
}
],
"lastModified": "2026-09-24T16:17:21.640",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}