CVE-2026-74484 (GCVE-0-2026-74484)
Vulnerability from cvelistv5
Published
2026-08-15 12:27
Modified
2026-08-19 06:52
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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:
binfmt_misc sb -> inode -> entry -> interp_file -> vfsmount -> binfmt_misc sb
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:
- 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.
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.
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.
References
| URL | Tags | |
|---|---|---|
Impacted products
{
"containers": {
"cna": {
"affected": [
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"product": "Linux",
"programFiles": [
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],
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},
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],
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"versions": [
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"version": "6.7"
},
{
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"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.103",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.44",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver"
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{
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"version": "7.2",
"versionType": "original_commit_for_fix"
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"cpeApplicability": [
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{
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: don\u0027t let an \u0027F\u0027 entry pin its own instance\n\nAn entry registered with \u0027F\u0027 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 -\u003e inode -\u003e entry -\u003e interp_file -\u003e vfsmount -\u003e 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\u0027s a DoS. And it isn\u0027t only the superblock that leaks. It pins the\nuser namespace it was mounted in, so every iteration permanently eats\none of the caller\u0027s user namespace charges.\n\nSo let\u0027s just do the sane thing. SB_I_NOEXEC makes open_exec() fail on\nthe instance\u0027s 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 \u0027F\u0027 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\u0027t apply to those trees anyway.\n\nNote that SB_I_NODEV is implicitly raised for userns mounts but raise it\nexplicitly here as well."
}
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"providerMetadata": {
"dateUpdated": "2026-08-19T06:52:35.407Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/1cc2decee06acc939337304e9b3f737fd5d8c4bd"
},
{
"url": "https://git.kernel.org/stable/c/4dad8ca637d44d5a6d5c23fa80c9e2e455198c2b"
},
{
"url": "https://git.kernel.org/stable/c/098e92fe0f1bde5af99c8cf504f13f01ef139f85"
},
{
"url": "https://git.kernel.org/stable/c/79055d82772b9584f259b747fe40ff56a076678d"
}
],
"title": "binfmt_misc: don\u0027t let an \u0027F\u0027 entry pin its own instance",
"x_generator": {
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}
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"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74484",
"datePublished": "2026-08-15T12:27:16.346Z",
"dateReserved": "2026-08-15T05:44:03.904Z",
"dateUpdated": "2026-08-19T06:52:35.407Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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