futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()

{
  "id": "332b3a523416b3d3a507fd88f216309b57c02425d478d9b1c6fdea41123b670b",
  "url": "https://osv.dev/vulnerability/CVE-2026-23415",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy() During futex_key_to_node_opt() execution, vma->vm_policy is read under speculative mmap lock and RCU. Concurrently, mbind() may call vma_replace_policy() which frees the old mempolicy immediately via kmem_cache_free(). This creates a race where __futex_key_to_node() dereferences a freed mempolicy pointer, causing a use-after-free read of mpol->mode. [ 151.412631] BUG: KASAN: slab-use-after-free in __futex_key_to_node (kernel/futex/core.c:349) [ 151.414046] Read of size 2 at addr ffff888001c49634 by task e/87 [ 151.415969] Call Trace: [ 151.416732] __asan_load2 (mm/kasan/generic.c:271) [ 151.416777] __futex_key_to_node (kernel/futex/core.c:349) [ 151.416822] get_futex_key (kernel/futex/core.c:374 kernel/futex/core.c:386 kernel/futex/core.c:593) Fix by adding rcu to __mpol_put().",
    "evidence": "osv:CVE-2026-23415",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.21",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.11",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-23415",
      "aliases": [
        "CVE-2026-23415"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "c042c505210dc3453f378df432c10fff3d471bc5"
                },
                {
                  "fixed": "853f70c67d1b37e368fdcb3e328c4b8c04f53ac0"
                },
                {
                  "fixed": "7e196194ea27bd49adf3551e2aceb83498eb73fe"
                },
                {
                  "fixed": "190a8c48ff623c3d67cb295b4536a660db2012aa"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23415.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.16.0"
                },
                {
                  "fixed": "6.18.21"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.11"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23415.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:21.069319781Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/190a8c48ff623c3d67cb295b4536a660db2012aa",
        "https://git.kernel.org/stable/c/7e196194ea27bd49adf3551e2aceb83498eb73fe",
        "https://git.kernel.org/stable/c/853f70c67d1b37e368fdcb3e328c4b8c04f53ac0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23415.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23415",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23415.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-23415",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 487360,
  "published_at": "2026-04-02T11:40:56.476+00:00"
}