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CVE-2026-89793 affecting package kernel 6.6.157.1-1

Type: advisorySource: OSV1 source record

In the Linux kernel, the following vulnerability has been resolved: ublk: clear VM_MAYWRITE on read-only ublk char device mmap ublk_ch_mmap() rejects mmap requests with VM_WRITE set, but never clears VM_MAYWRITE on the resulting read-only mapping. This allows a userspace daemon to mmap the per-queue command buffer PROT_READ, then upgrade it to PROT_WRITE via mprotect(), since VM_MAYWRITE was never cleared. The command buffer holds struct ublksrv_io_desc entries that are kernel-written ABI; a writable mapping lets an unprivileged daemon process corrupt fields such as addr, op_flags, nr_sectors, and start_sector. Same bug class as the drm/panthor and drm/vc4 VM_MAYWRITE fixes, and the 2026-08-13 ptp/vmclock fix (a5edadbae57e). Verified via mprotect() PoC: before the fix, a PROT_READ mapping can be upgraded to PROT_READ|PROT_WRITE and a write into the command buffer corrupts io_desc fields (confirmed under KASAN). After the fix, mprotect() returns -EACCES.

Announced Source revision 1
Original source ↗

AZL-101334

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:AZL-101334

kernel

Source reference: /affected/0/package/name

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "last_affected": "6.6.157.1-1"
          }
        ]
      }
    ],
    "package": {
      "name": "kernel",
      "purl": "pkg:rpm/azure-linux/kernel",
      "ecosystem": "Azure Linux:3"
    },
    "database_specific": {
      "source": "https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-101334.json"
    }
  }
]
Related CVEs
CVE-2026-89793

Source reference: /upstream

Publisher severity

No explicit severity was provided.

Linked CVE context

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CVE-2026-89793 · High

Linux, Linux

Event
#83652 · Revision 1
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