{
  "cveId": "CVE-2026-99256",
  "url": "https://patchblox.com/security/cve/CVE-2026-99256",
  "summary": "CVE-2026-99256 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-99256, released November 3, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "dm cache: fix issue with background work locking",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  dm cache: fix issue with background work locking  dm cache used a rw_semaphore for background_work_lock. Write locks on rw_semaphores have strict owner semantics, but there was no guarantee that the process that locked background_work_lock was the same process that unlocked it. This can be easily seen using a kernel compiled with CONFIG_DEBUG_RWSEMS. Given a dm cache device \u003Ccache\u003E, run: \u0027dmsetup suspend \u003Ccache\u003E \u0026\u0026 dmsetup resume \u003Ccache\u003E\u0027. This will trigger a kernel warning:  DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) \u0026\u0026 !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))  triggered by cache_resume(). To fix this, switch from a rw_semaphore to a spinlock and a wait queue. dm cache already has a wait queue and associated counter, migration_wait and nr_allocated_migrations, that was getting woken up when background work was getting completed, but wasn\u0027t actually used by anything. This is replaced by the background_work queue and counter.",
  "published": "2026-11-03T12:17:32Z",
  "severity": "Low",
  "cvss": 2.3,
  "epss": 0.00202,
  "epssPercentile": 0.10155,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-99256",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.115-1",
      "fix": "DEBIAN-CVE-2026-99256",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-99256",
      "released": "2026-11-03T18:58:21Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.13-1",
      "fix": "DEBIAN-CVE-2026-99256",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-99256",
      "released": "2026-11-03T18:58:21Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T06:59:42Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}