{"id":"CVE-2026-89793","summary":"ublk: clear VM_MAYWRITE on read-only ublk char device mmap","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nublk: clear VM_MAYWRITE on read-only ublk char device mmap\n\nublk_ch_mmap() rejects mmap requests with VM_WRITE set, but never\nclears VM_MAYWRITE on the resulting read-only mapping. This allows\na userspace daemon to mmap the per-queue command buffer PROT_READ,\nthen upgrade it to PROT_WRITE via mprotect(), since VM_MAYWRITE was\nnever cleared.\n\nThe command buffer holds struct ublksrv_io_desc entries that are\nkernel-written ABI; a writable mapping lets an unprivileged daemon\nprocess corrupt fields such as addr, op_flags, nr_sectors, and\nstart_sector.\n\nSame bug class as the drm/panthor and drm/vc4 VM_MAYWRITE fixes, and\nthe 2026-08-13 ptp/vmclock fix (a5edadbae57e).\n\nVerified via mprotect() PoC: before the fix, a PROT_READ mapping can\nbe upgraded to PROT_READ|PROT_WRITE and a write into the command\nbuffer corrupts io_desc fields (confirmed under KASAN). After the\nfix, mprotect() returns -EACCES.","modified":"2026-10-06T02:47:30.330314477Z","published":"2026-09-16T09:54:33.678Z","related":["openSUSE-SU-2026:11880-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89793.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/5befd06a72216869b607cf7724a4f16c6a2d3999"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6e2b571b0a54755b06e092501913e1dfefe75d6c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/be41733c24be58e2a1ef718c80fafdfb98a40d5e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e373c1acdbcf88cec533ece9f589020adaed0a78"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fa5e1bc673ca59722608af67b27e65dba0c97926"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89793.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89793"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"71f28f3136aff5890cd56de78abc673f8393cad9"},{"fixed":"be41733c24be58e2a1ef718c80fafdfb98a40d5e"},{"fixed":"5befd06a72216869b607cf7724a4f16c6a2d3999"},{"fixed":"e373c1acdbcf88cec533ece9f589020adaed0a78"},{"fixed":"fa5e1bc673ca59722608af67b27e65dba0c97926"},{"fixed":"6e2b571b0a54755b06e092501913e1dfefe75d6c"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-89793.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.0.0"},{"fixed":"6.6.157"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.51"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-89793.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}