{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2"
            },
            {
              "fixed": "be41733c24be58e2a1ef718c80fafdfb98a40d5e"
            },
            {
              "fixed": "5befd06a72216869b607cf7724a4f16c6a2d3999"
            },
            {
              "fixed": "e373c1acdbcf88cec533ece9f589020adaed0a78"
            },
            {
              "fixed": "fa5e1bc673ca59722608af67b27e65dba0c97926"
            },
            {
              "fixed": "6e2b571b0a54755b06e092501913e1dfefe75d6c"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.6.157"
            },
            {
              "fixed": "6.12.110"
            },
            {
              "fixed": "6.18.51"
            },
            {
              "fixed": "7.2.5"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "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"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89793.json"
  },
  "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.",
  "id": "CVE-2026-89793",
  "modified": "2026-09-18T03:31:00.141292918Z",
  "published": "2026-09-16T09:54:33.678Z",
  "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"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ublk: clear VM_MAYWRITE on read-only ublk char device mmap"
}