CVE-2026-74485 (GCVE-0-2026-74485)
Vulnerability from cvelistv5
Published
2026-08-15 12:27
Modified
2026-08-19 16:37
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
binfmt_misc: reject a flag character as the field delimiter
The registration string starts with a user chosen delimiter that
separates the individual fields. So that the field parsers terminate
even on a truncated string create_entry() pads the buffer with that
same delimiter:
memset(buf + count, del, 8);
Most fields are scanned for the delimiter with strchr()/scanarg() and
happily stop on the padding. The flags field is different: instead of
scanning for the delimiter check_special_flags() consumes the flag
characters 'P', 'O', 'C' and 'F' and stops at the first byte that is
none of them, relying on the trailing delimiter to end the scan.
If the delimiter is itself a flag character the padding no longer acts
as a terminator. The scan swallows all eight padding bytes and keeps
reading past the end of the allocation until it hits a byte that is
not a flag character. For example registering
PaPEPPxPPiP
with 'P' as the delimiter (name "a", type extension, magic "x",
interpreter "i", empty flags) leaves the flag scan running off the end
of the buffer. The registration is rejected in the end because the
parser does not stop exactly at buf + count, but only after the out of
bounds read has already happened. With an unlucky allocation layout the
scan can walk into an unmapped page; under KASAN it is reported as a
slab out of bounds read. binfmt_misc mounts are available to
unprivileged users in a user namespace so the read is reachable without
privileges.
Reject a delimiter that is one of the flag characters up front. Such a
registration was always rejected anyway, only after the out of bounds
read, so no valid registration string changes meaning.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/binfmt_misc.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "9970e094e5d60f0d66914bf9a97d1ef19107ebf5",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
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"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
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{
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"status": "affected",
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"versionType": "git"
},
{
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"status": "affected",
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"versionType": "git"
}
]
},
{
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"product": "Linux",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.12"
},
{
"lessThan": "2.6.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.265",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.151",
"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"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.265",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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},
{
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: reject a flag character as the field delimiter\n\nThe registration string starts with a user chosen delimiter that\nseparates the individual fields. So that the field parsers terminate\neven on a truncated string create_entry() pads the buffer with that\nsame delimiter:\n\n\tmemset(buf + count, del, 8);\n\nMost fields are scanned for the delimiter with strchr()/scanarg() and\nhappily stop on the padding. The flags field is different: instead of\nscanning for the delimiter check_special_flags() consumes the flag\ncharacters \u0027P\u0027, \u0027O\u0027, \u0027C\u0027 and \u0027F\u0027 and stops at the first byte that is\nnone of them, relying on the trailing delimiter to end the scan.\n\nIf the delimiter is itself a flag character the padding no longer acts\nas a terminator. The scan swallows all eight padding bytes and keeps\nreading past the end of the allocation until it hits a byte that is\nnot a flag character. For example registering\n\n\tPaPEPPxPPiP\n\nwith \u0027P\u0027 as the delimiter (name \"a\", type extension, magic \"x\",\ninterpreter \"i\", empty flags) leaves the flag scan running off the end\nof the buffer. The registration is rejected in the end because the\nparser does not stop exactly at buf + count, but only after the out of\nbounds read has already happened. With an unlucky allocation layout the\nscan can walk into an unmapped page; under KASAN it is reported as a\nslab out of bounds read. binfmt_misc mounts are available to\nunprivileged users in a user namespace so the read is reachable without\nprivileges.\n\nReject a delimiter that is one of the flag characters up front. Such a\nregistration was always rejected anyway, only after the out of bounds\nread, so no valid registration string changes meaning."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.1,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - Exploitation requires a local write() to binfmt_misc/register via bm_register_write()-\u003ecreate_entry(); the path is a VFS syscall on a mounted filesystem, not any network protocol or remote packet handler.\nAC:L - An attacker fully controls the registration string and can deterministically choose delimiter P/O/C/F with empty flags so check_special_flags() consumes padding and reads past the kmalloc buffer on every attempt; no race or victim-specific state is required.\nPR:L - binfmt_misc has FS_USERNS_MOUNT; an unprivileged local user can unshare a user namespace, mount binfmt_misc, and write register without init-namespace root, matching the fix commit\u0027s stated unprivileged reachability.\nUI:N - Triggering is entirely attacker-driven through mounting binfmt_misc and writing a crafted registration string; no victim must open files, click links, or perform any interactive action beyond the attacker\u0027s own syscalls.\nS:U - The slab out-of-bounds read and any disclosed kernel data remain within the host kernel security authority; this is standard local kernel memory access, not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:H - check_special_flags() scans past buf+count+8 through adjacent kmalloc/slab memory until a non-P/O/C/F byte, a classic out-of-bounds read that can disclose kernel pointers and other sensitive heap contents for KASLR defeat.\nI:N - The defect is read-only: check_special_flags() only dereferences bytes beyond the allocation and sets flags on the soon-freed Node; it performs no out-of-bounds write, metadata corruption, or control-flow hijack primitive.\nA:H - The unbounded flag scan can walk into an unmapped page and fault the kernel; KASAN reports slab-out-of-bounds, and the single write() to register is trivially repeatable for denial-of-service."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:37:40.898Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/96bd5d4fea2970b9b08265293ca7a10b9b27c0fd"
},
{
"url": "https://git.kernel.org/stable/c/9970e094e5d60f0d66914bf9a97d1ef19107ebf5"
},
{
"url": "https://git.kernel.org/stable/c/b29e3c1f375c1296362d219ff38bceddf2d2a88a"
},
{
"url": "https://git.kernel.org/stable/c/1819f82dee766c58295ecaacdac02cdf6837d7a4"
},
{
"url": "https://git.kernel.org/stable/c/1853e95c9bfe69ef1dd862b3f551e68f4a1b76cc"
},
{
"url": "https://git.kernel.org/stable/c/840bb9c49c3e75fb32b593d67ab32f6b77122262"
},
{
"url": "https://git.kernel.org/stable/c/9a2d87db3898b5993b64fd258d0334e0eba9ee0d"
},
{
"url": "https://git.kernel.org/stable/c/8e85d50ba1117fd446bf9a250bd8a97d48384bdc"
}
],
"title": "binfmt_misc: reject a flag character as the field delimiter",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74485",
"datePublished": "2026-08-15T12:27:16.980Z",
"dateReserved": "2026-08-15T05:44:03.905Z",
"dateUpdated": "2026-08-19T16:37:40.898Z",
"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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