{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "59b57717fff8b562825d9d25e0180ad7e8048ca9"
            },
            {
              "fixed": "23acef4156c260e8598397a1a2e8b3a23e919893"
            },
            {
              "fixed": "1bd36e93b542d9dd020190c6607c6a3663405195"
            },
            {
              "fixed": "740ba1ebb223f137ff088ab74d533a13f9167bd8"
            },
            {
              "fixed": "115a5266749dcde7fe4127e8623d19c752088f69"
            },
            {
              "fixed": "dfc8292a1d6782c76b626315605e0585a5a18447"
            },
            {
              "fixed": "ea3af09eb87d8f8708c66747fcf1a2762902e839"
            },
            {
              "fixed": "50879a3c1faf06e661090015d59e2127255cff27"
            },
            {
              "fixed": "67cb119d32f35e32acd0393bbeb318b2bb1fdafe"
            },
            {
              "fixed": "8f5857be99f1ed1fa80991c72449541f634626ee"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.19.0"
            },
            {
              "fixed": "5.10.258"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.11.0"
            },
            {
              "fixed": "5.15.209"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.16.0"
            },
            {
              "fixed": "6.1.175"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.2.0"
            },
            {
              "fixed": "6.6.136"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.83"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.24"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "6.19.14"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.20.0"
            },
            {
              "fixed": "7.0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31586.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: blk-cgroup: fix use-after-free in cgwb_release_workfn()\n\ncgwb_release_workfn() calls css_put(wb-\u003eblkcg_css) and then later accesses\nwb-\u003eblkcg_css again via blkcg_unpin_online().  If css_put() drops the last\nreference, the blkcg can be freed asynchronously (css_free_rwork_fn -\u003e\nblkcg_css_free -\u003e kfree) before blkcg_unpin_online() dereferences the\npointer to access blkcg-\u003eonline_pin, resulting in a use-after-free:\n\n  BUG: KASAN: slab-use-after-free in blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367)\n  Write of size 4 at addr ff11000117aa6160 by task kworker/71:1/531\n   Workqueue: cgwb_release cgwb_release_workfn\n   Call Trace:\n    \u003cTASK\u003e\n     blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367)\n     cgwb_release_workfn (mm/backing-dev.c:629)\n     process_scheduled_works (kernel/workqueue.c:3278 kernel/workqueue.c:3385)\n\n   Freed by task 1016:\n    kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6246 mm/slub.c:6561)\n    css_free_rwork_fn (kernel/cgroup/cgroup.c:5542)\n    process_scheduled_works (kernel/workqueue.c:3302 kernel/workqueue.c:3385)\n\n** Stack based on commit 66672af7a095 (\"Add linux-next specific files\nfor 20260410\")\n\nI am seeing this crash sporadically in Meta fleet across multiple kernel\nversions.  A full reproducer is available at:\nhttps://github.com/leitao/debug/blob/main/reproducers/repro_blkcg_uaf.sh\n\n(The race window is narrow.  To make it easily reproducible, inject a\nmsleep(100) between css_put() and blkcg_unpin_online() in\ncgwb_release_workfn().  With that delay and a KASAN-enabled kernel, the\nreproducer triggers the splat reliably in less than a second.)\n\nFix this by moving blkcg_unpin_online() before css_put(), so the\ncgwb's CSS reference keeps the blkcg alive while blkcg_unpin_online()\naccesses it.",
  "id": "CVE-2026-31586",
  "modified": "2026-07-08T05:36:02.056341458Z",
  "published": "2026-04-24T14:42:14.937Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/115a5266749dcde7fe4127e8623d19c752088f69"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1bd36e93b542d9dd020190c6607c6a3663405195"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/23acef4156c260e8598397a1a2e8b3a23e919893"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/50879a3c1faf06e661090015d59e2127255cff27"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/67cb119d32f35e32acd0393bbeb318b2bb1fdafe"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/740ba1ebb223f137ff088ab74d533a13f9167bd8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8f5857be99f1ed1fa80991c72449541f634626ee"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dfc8292a1d6782c76b626315605e0585a5a18447"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ea3af09eb87d8f8708c66747fcf1a2762902e839"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31586.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31586"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.7.5",
  "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": "mm: blk-cgroup: fix use-after-free in cgwb_release_workfn()"
}