CVE-2025-39992
In the Linux kernel, the following vulnerability has been resolved:
mm: swap: check for stable address space before operating on the VMA
It is possible to hit a zero entry while traversing the vmas in unuse_mm() called from swapoff path and accessing it causes the OOPS:
The issue is manifested from the below race between the fork() on a process and swapoff: fork(dup_mmap()) swapoff(unuse_mm) --------------- ----------------- 1) Identical mtree is built using __mt_dup().
3) Fatal signal is sent to the parent process(which is the current during the fork) thus skip the duplication of the vmas and mark the vma range with XA_ZERO_ENTRY as a marker for this process that helps during exit_mmap().
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4) swapoff is tried on the 'mm' added to the 'mmlist' as part of the 2.
5) unuse_mm(), that iterates through the vma's of this 'mm' will hit the non-NULL zero entry and operating on this zero entry as a vma is resulting into the oops.
The proper fix would be around not exposing this partially-valid tree to others when droping the mmap lock, which is being solved with [1]. A simpler solution would be checking for MMF_UNSTABLE, as it is set if mm_struct is not fully initialized in dup_mmap().
Thanks to Liam/Lorenzo/David for all the suggestions in fixing this issue.
Detalles técnicos trazas, registros y código del informe original
Unable to handle kernel NULL pointer dereference at virtual address
0000000000000446--> Loading the memory from offset 0x40 on the
XA_ZERO_ENTRY as address.
Mem abort info:
ESR = 0x0000000096000005
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x05: level 1 translation fault
2) copy_pte_range()-->
copy_nonpresent_pte():
The dst mm is added into the
mmlist to be visible to the
swapoff operation.CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2025-39992",
"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": "d2406291483775ecddaee929231a39c70c08fda2",
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"versionType": "git"
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{
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"versionType": "git"
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{
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{
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"versionType": "git"
}
],
"programFiles": [
"mm/swapfile.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.8"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.8",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.51",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.16.11",
"versionType": "semver",
"lessThanOrEqual": "6.16.*"
},
{
"status": "unaffected",
"version": "6.17.1",
"versionType": "semver",
"lessThanOrEqual": "6.17.*"
},
{
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"mm/swapfile.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2025-10-15T08:15:37.317",
"references": [
{
"url": "https://git.kernel.org/stable/c/1367da7eb875d01102d2ed18654b24d261ff5393",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/4e5f060d7347466f77aaff1c0d5a6c4f1fb217ac",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
"url": "https://git.kernel.org/stable/c/9cddad3b26dac830407d2d3c0de5205ff6d6dda0",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/e4e99d69b8b8295c501b2eef89e13306b738b667",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Deferred",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: swap: check for stable address space before operating on the VMA\n\nIt is possible to hit a zero entry while traversing the vmas in unuse_mm()\ncalled from swapoff path and accessing it causes the OOPS:\n\nUnable to handle kernel NULL pointer dereference at virtual address\n0000000000000446--> Loading the memory from offset 0x40 on the\nXA_ZERO_ENTRY as address.\nMem abort info:\n ESR = 0x0000000096000005\n EC = 0x25: DABT (current EL), IL = 32 bits\n SET = 0, FnV = 0\n EA = 0, S1PTW = 0\n FSC = 0x05: level 1 translation fault\n\nThe issue is manifested from the below race between the fork() on a\nprocess and swapoff:\nfork(dup_mmap())\t\t\tswapoff(unuse_mm)\n--------------- -----------------\n1) Identical mtree is built using\n __mt_dup().\n\n2) copy_pte_range()-->\n\tcopy_nonpresent_pte():\n The dst mm is added into the\n mmlist to be visible to the\n swapoff operation.\n\n3) Fatal signal is sent to the parent\nprocess(which is the current during the\nfork) thus skip the duplication of the\nvmas and mark the vma range with\nXA_ZERO_ENTRY as a marker for this process\nthat helps during exit_mmap().\n\n\t\t\t\t 4) swapoff is tried on the\n\t\t\t\t\t'mm' added to the 'mmlist' as\n\t\t\t\t\tpart of the 2.\n\n\t\t\t\t 5) unuse_mm(), that iterates\n\t\t\t\t\tthrough the vma's of this 'mm'\n\t\t\t\t\twill hit the non-NULL zero entry\n\t\t\t\t\tand operating on this zero entry\n\t\t\t\t\tas a vma is resulting into the\n\t\t\t\t\toops.\n\nThe proper fix would be around not exposing this partially-valid tree to\nothers when droping the mmap lock, which is being solved with [1]. A\nsimpler solution would be checking for MMF_UNSTABLE, as it is set if\nmm_struct is not fully initialized in dup_mmap().\n\nThanks to Liam/Lorenzo/David for all the suggestions in fixing this\nissue."
}
],
"lastModified": "2026-06-17T09:18:58.383",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}