CVE-2026-80550 (GCVE-0-2026-80550)
Vulnerability from cvelistv5
Published
2026-08-26 14:37
Modified
2026-08-27 05:01
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
s390/vfio_ccw: Fix out of bounds check on CCW array
The routine ccwchain_calc_length() counts the number of channel
command words (CCWs) that are chained together in a single channel
program, and rejects anything larger than CCWCHAIN_LEN_MAX (256) CCWs.
The loop itself is "do..while (count < 257)", and while the logic in
is_cpa_within_range() correctly adjusts between the 0-index array of
CCWs and the count of CCWs starting at 1, this means it would look
at a possible 257th CCW before ending the loop and (correctly)
returning an error.
Fix this by restructuring the loop to break as soon as 256 CCWs
(thus indexes 0-255) are examined, without looking at memory
outside the range.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c Version: 0a19e61e6d4c6192077ead760ba0a2d350987d4c |
||
{
"containers": {
"cna": {
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{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"drivers/s390/cio/vfio_ccw_cp.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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{
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]
},
{
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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": "4.12"
},
{
"lessThan": "4.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.266",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.217",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.184",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.153",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.46",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.10",
"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": "5.10.266",
"versionStartIncluding": "4.12",
"vulnerable": true
},
{
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},
{
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{
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{
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},
{
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{
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio_ccw: Fix out of bounds check on CCW array\n\nThe routine ccwchain_calc_length() counts the number of channel\ncommand words (CCWs) that are chained together in a single channel\nprogram, and rejects anything larger than CCWCHAIN_LEN_MAX (256) CCWs.\n\nThe loop itself is \"do..while (count \u003c 257)\", and while the logic in\nis_cpa_within_range() correctly adjusts between the 0-index array of\nCCWs and the count of CCWs starting at 1, this means it would look\nat a possible 257th CCW before ending the loop and (correctly)\nreturning an error.\n\nFix this by restructuring the loop to break as soon as 256 CCWs\n(thus indexes 0-255) are examined, without looking at memory\noutside the range."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.9,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The bug is reached only via local VFIO-ccw mediated-device write() on the I/O region (guest channel program relayed by QEMU into fsm_io_request\u2192cp_init\u2192ccwchain_calc_length); vfio-ccw has no network, adjacent-radio, or physical-bus entry point.\nAC:L - An attacker fully controls guest channel program content and can reliably submit 256 command-chained CCWs so ccwchain_calc_length() reaches the 257th iteration; no race, special timing, or uncontrollable heap layout is required beyond crafting the CCW chain.\nPR:N - A malicious KVM guest with an assigned vfio-ccw mediated subchannel needs no host credentials or capabilities; it triggers the bug by issuing normal guest I/O that QEMU forwards through VFIO, without init-namespace root or admin setup privileges at exploit time.\nUI:N - Exploitation requires only the attacker\u0027s own channel program submission through VFIO passthrough I/O once the device is assigned; no separate victim mount, click, or other user action is needed.\nS:C - Guest-supplied channel programs are parsed in the host kernel cp_init() path during vfio-ccw device passthrough on IBM Z/LinuxONE, so the out-of-bounds read crosses the guest-to-host VFIO virtualization boundary and can compromise hypervisor memory outside the VM security scope.\nC:H - ccwchain_calc_length() reads one struct ccw1 (8 bytes) past the 256-element guest_cp kmalloc buffer when all CCWs are chained, constituting a kernel heap out-of-bounds read of adjacent slab memory that per kernel guidance enables information disclosure primitives.\nI:N - The vulnerability is a single out-of-bounds read used only for chain/TIC validation before returning -EINVAL; it performs no out-of-bounds write and does not modify host or guest data, channel program state, or kernel control structures on the error path.\nA:L - The out-of-bounds read typically does not crash production kernels because the access stays within the same kmalloc slab page, but KASAN-instrumented or hardened builds can detect it and fault; availability impact is limited rather than a reliable host panic."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-27T05:01:38.029Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/0282fb1c4b638eecfe2cc558092c460911d8f7e2"
},
{
"url": "https://git.kernel.org/stable/c/907adc667d902fafbdb2d740d57b55bd025dc4cd"
},
{
"url": "https://git.kernel.org/stable/c/f20be33d093ce7630c17ff7ed93caf7eaf8ac1a3"
},
{
"url": "https://git.kernel.org/stable/c/af3f80ca4c8b17f20f9e588def076288fdb49e65"
},
{
"url": "https://git.kernel.org/stable/c/499a8a66b1598bfab97182aed15e0f1646074a3d"
},
{
"url": "https://git.kernel.org/stable/c/4c2e1d359d7a2b82cdf3254e4e480af9417f99fb"
},
{
"url": "https://git.kernel.org/stable/c/d5d096cd9369e986d4e5153baa86b8b35c283e09"
},
{
"url": "https://git.kernel.org/stable/c/a005b7f1a491ffda61bff0fd0f6548f8986fb977"
}
],
"title": "s390/vfio_ccw: Fix out of bounds check on CCW array",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-80550",
"datePublished": "2026-08-26T14:37:19.956Z",
"dateReserved": "2026-08-26T14:34:25.766Z",
"dateUpdated": "2026-08-27T05:01:38.029Z",
"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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