CVE-2026-74484
In the Linux kernel, the following vulnerability has been resolved:
binfmt_misc: don't let an 'F' entry pin its own instance
An entry registered with 'F' opens its interpreter at registration time and holds that file until the entry is freed. Any entry nobody removes by hand only gets closed once the binfmt_misc superblock is shut down. If the interpreter lives on a mount that keeps that superblock alive the two pin each other:
TL;DR the file is never closed. Once the mount namespace is gone there is nothing left to unregister through either.
There are two ways to trigger this bug:
That's a DoS. And it isn't only the superblock that leaks. It pins the user namespace it was mounted in, so every iteration permanently eats one of the caller's user namespace charges.
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So let's just do the sane thing. SB_I_NOEXEC makes open_exec() fail on the instance's own files and s_stack_depth makes overlayfs reject the layer before it ever takes a clone. That also covers the ecryptfs and fuse passthrough variants. What 'F' promises is unchanged.
The stable tag is narrower than the Fixes tags on purpose. Before sandboxed mounts this needed global root against the single instance everyone shares, and the change doesn't apply to those trees anyway.
Note that SB_I_NODEV is implicitly raised for userns mounts but raise it explicitly here as well.
Detalles técnicos trazas, registros y código del informe original
binfmt_misc sb -> inode -> entry -> interp_file -> vfsmount -> binfmt_misc sb - Point the interpreter at the instance itself. Its files are regular files owned by the mounter and both bm_get_inode() and simple_fill_super() leave i_op at empty_iops. So notify_change() falls back to simple_setattr() and chmod +x works. We never set SB_I_NOEXEC and so open_exec() accepts it. - Use the instance as an overlayfs lower layer. The overlay superblock holds a clone_private_mount() of every layer until it is destroyed and that clone is in no namespace. So umount_tree() never reaches it.
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: 0.21%
- Percentil entre todas las CVEs puntuadas: 10
- Fecha de la puntuación: 5/10/2026
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)
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{
"id": "CVE-2026-74484",
"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": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"lessThan": "1cc2decee06acc939337304e9b3f737fd5d8c4bd",
"versionType": "git"
},
{
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"lessThan": "4dad8ca637d44d5a6d5c23fa80c9e2e455198c2b",
"versionType": "git"
},
{
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"lessThan": "098e92fe0f1bde5af99c8cf504f13f01ef139f85",
"versionType": "git"
},
{
"status": "affected",
"version": "21ca59b365c091d583f36ac753eaa8baf947be6f",
"lessThan": "79055d82772b9584f259b747fe40ff56a076678d",
"versionType": "git"
}
],
"programFiles": [
"fs/binfmt_misc.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.7"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.7",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.103",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.44",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/binfmt_misc.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-15T13:17:53.270",
"references": [
{
"url": "https://git.kernel.org/stable/c/098e92fe0f1bde5af99c8cf504f13f01ef139f85",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/1cc2decee06acc939337304e9b3f737fd5d8c4bd",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/4dad8ca637d44d5a6d5c23fa80c9e2e455198c2b",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/79055d82772b9584f259b747fe40ff56a076678d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: don't let an 'F' entry pin its own instance\n\nAn entry registered with 'F' opens its interpreter at registration time\nand holds that file until the entry is freed. Any entry nobody removes\nby hand only gets closed once the binfmt_misc superblock is shut down.\nIf the interpreter lives on a mount that keeps that superblock alive the\ntwo pin each other:\n\n binfmt_misc sb -> inode -> entry -> interp_file -> vfsmount -> binfmt_misc sb\n\nTL;DR the file is never closed. Once the mount namespace is gone there\nis nothing left to unregister through either.\n\nThere are two ways to trigger this bug:\n\n- Point the interpreter at the instance itself. Its files are regular\n files owned by the mounter and both bm_get_inode() and\n simple_fill_super() leave i_op at empty_iops. So notify_change() falls\n back to simple_setattr() and chmod +x works. We never set SB_I_NOEXEC\n and so open_exec() accepts it.\n\n- Use the instance as an overlayfs lower layer. The overlay superblock\n holds a clone_private_mount() of every layer until it is destroyed and\n that clone is in no namespace. So umount_tree() never reaches it.\n\nThat's a DoS. And it isn't only the superblock that leaks. It pins the\nuser namespace it was mounted in, so every iteration permanently eats\none of the caller's user namespace charges.\n\nSo let's just do the sane thing. SB_I_NOEXEC makes open_exec() fail on\nthe instance's own files and s_stack_depth makes overlayfs reject the\nlayer before it ever takes a clone. That also covers the ecryptfs and\nfuse passthrough variants. What 'F' promises is unchanged.\n\nThe stable tag is narrower than the Fixes tags on purpose. Before\nsandboxed mounts this needed global root against the single instance\neveryone shares, and the change doesn't apply to those trees anyway.\n\nNote that SB_I_NODEV is implicitly raised for userns mounts but raise it\nexplicitly here as well."
}
],
"lastModified": "2026-08-19T07:16:55.913",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}