{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80550","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-08-26T14:34:25.766Z","datePublished":"2026-08-26T14:37:19.956Z","dateUpdated":"2026-08-27T05:01:38.029Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-27T05:01:38.029Z"},"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 < 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":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L","baseScore":7.9,"baseSeverity":"HIGH"},"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→cp_init→ccwchain_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's 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."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/s390/cio/vfio_ccw_cp.c"],"versions":[{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"0282fb1c4b638eecfe2cc558092c460911d8f7e2","status":"affected","versionType":"git"},{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"907adc667d902fafbdb2d740d57b55bd025dc4cd","status":"affected","versionType":"git"},{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"f20be33d093ce7630c17ff7ed93caf7eaf8ac1a3","status":"affected","versionType":"git"},{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"af3f80ca4c8b17f20f9e588def076288fdb49e65","status":"affected","versionType":"git"},{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"499a8a66b1598bfab97182aed15e0f1646074a3d","status":"affected","versionType":"git"},{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"4c2e1d359d7a2b82cdf3254e4e480af9417f99fb","status":"affected","versionType":"git"},{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"d5d096cd9369e986d4e5153baa86b8b35c283e09","status":"affected","versionType":"git"},{"version":"0a19e61e6d4c6192077ead760ba0a2d350987d4c","lessThan":"a005b7f1a491ffda61bff0fd0f6548f8986fb977","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/s390/cio/vfio_ccw_cp.c"],"versions":[{"version":"4.12","status":"affected"},{"version":"0","lessThan":"4.12","status":"unaffected","versionType":"semver"},{"version":"5.10.266","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.217","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.184","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.153","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.105","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.46","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.10","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"5.10.266"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"5.15.217"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.1.184"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.6.153"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.12.105"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.18.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"7.1.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"7.2"}]}]}],"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"}}}}