FKIE_CVE-2026-63809

Vulnerability from fkie_nvd - Published: 2026-07-19 12:16 - Updated: 2026-10-19 20:19
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: use kvfree() for replaced sysctl write buffer proc_sys_call_handler() allocates its temporary sysctl buffer with kvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since kvzalloc() may fall back to vmalloc() for large allocations, freeing that buffer with kfree() is wrong and can corrupt memory. Use kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc allocations. The bug was first flagged by an experimental analysis tool we are developing for kernel memory-management bugs while analyzing v6.13-rc1. The tool is still under development and is not yet publicly available. Manual inspection confirms that the bug is still present in v7.1-rc5. Reproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with KASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the test tree also included the accompanying fix for the stale ret == 1 check in __cgroup_bpf_run_filter_sysctl(). The reproducer confines failslab injections to the proc_sys_call_handler() range, uses stacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to /proc/sys/kernel/domainname from a task in the target cgroup. Under that setup, fail-nth=1 triggered the fault: BUG: unable to handle page fault for address: ffffeb0200024d48 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 SMP KASAN NOPTI CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:kfree+0x6e/0x510 ... Call Trace: <TASK> ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30 __cgroup_bpf_run_filter_sysctl+0x74d/0xc30 ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? __kvmalloc_node_noprof+0x345/0x870 ? proc_sys_call_handler+0x250/0x480 ? srso_return_thunk+0x5/0x5f proc_sys_call_handler+0x3a2/0x480 ? __pfx_proc_sys_call_handler+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? selinux_file_permission+0x39f/0x500 ? srso_return_thunk+0x5/0x5f ? lock_is_held_type+0x9e/0x120 vfs_write+0x98e/0x1000 ... </TASK> With this fix applied on top of the same test setup, rerunning the reproducer with fail-nth=1 yields no corresponding Oops reports.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4c21b5927d4364bfe7365f2700da5fea0ed0d004
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/65bd0c0afb0e1bf3287458e342429b069624f7d4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/70df4de46577fab5e25418f014583155a147c902
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/81fc9a13acae99966232f0e055eb2e445263b89a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/838fe9c28121777c59a9406710a68fcf77bb8017
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/cgroup.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e",
              "status": "affected",
              "version": "b7925acd82926ebbf94a0f0783a3961f4e558856",
              "versionType": "git"
            },
            {
              "lessThan": "77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2",
              "status": "affected",
              "version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
              "versionType": "git"
            },
            {
              "lessThan": "e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2",
              "status": "affected",
              "version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
              "versionType": "git"
            },
            {
              "lessThan": "81fc9a13acae99966232f0e055eb2e445263b89a",
              "status": "affected",
              "version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
              "versionType": "git"
            },
            {
              "lessThan": "838fe9c28121777c59a9406710a68fcf77bb8017",
              "status": "affected",
              "version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
              "versionType": "git"
            },
            {
              "lessThan": "65bd0c0afb0e1bf3287458e342429b069624f7d4",
              "status": "affected",
              "version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
              "versionType": "git"
            },
            {
              "lessThan": "70df4de46577fab5e25418f014583155a147c902",
              "status": "affected",
              "version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
              "versionType": "git"
            },
            {
              "lessThan": "4c21b5927d4364bfe7365f2700da5fea0ed0d004",
              "status": "affected",
              "version": "4508943794efdd94171549c0bd52810e2f4ad9fe",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "66258ab303588936ee1ee0794d9a271be24f73cb",
              "versionType": "git"
            },
            {
              "lessThan": "5.10.260",
              "status": "affected",
              "version": "5.10.20",
              "versionType": "semver"
            },
            {
              "lessThan": "5.12",
              "status": "affected",
              "version": "5.11.3",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/cgroup.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.12"
            },
            {
              "lessThan": "5.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.260",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.211",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.177",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.144",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.95",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.38",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: use kvfree() for replaced sysctl write buffer\n\nproc_sys_call_handler() allocates its temporary sysctl buffer with\nkvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since\nkvzalloc() may fall back to vmalloc() for large allocations, freeing\nthat buffer with kfree() is wrong and can corrupt memory.\n\nUse kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc\nallocations.\n\nThe bug was first flagged by an experimental analysis tool we are\ndeveloping for kernel memory-management bugs while analyzing\nv6.13-rc1. The tool is still under development and is not yet publicly\navailable. Manual inspection confirms that the bug is still\npresent in v7.1-rc5.\n\nReproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with\nKASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the\ntest tree also included the accompanying fix for the stale ret == 1\ncheck in __cgroup_bpf_run_filter_sysctl(). The reproducer confines\nfailslab injections to the proc_sys_call_handler() range, uses\nstacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to\n/proc/sys/kernel/domainname from a task in the target cgroup. Under\nthat setup, fail-nth=1 triggered the fault:\n\n  BUG: unable to handle page fault for address: ffffeb0200024d48\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 0 P4D 0\n  Oops: Oops: 0000  SMP KASAN NOPTI\n  CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4  PREEMPT(lazy)\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014\n  RIP: 0010:kfree+0x6e/0x510\n  ...\n  Call Trace:\n   \u003cTASK\u003e\n   ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30\n   __cgroup_bpf_run_filter_sysctl+0x74d/0xc30\n   ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10\n   ? srso_return_thunk+0x5/0x5f\n   ? __kvmalloc_node_noprof+0x345/0x870\n   ? proc_sys_call_handler+0x250/0x480\n   ? srso_return_thunk+0x5/0x5f\n   proc_sys_call_handler+0x3a2/0x480\n   ? __pfx_proc_sys_call_handler+0x10/0x10\n   ? srso_return_thunk+0x5/0x5f\n   ? selinux_file_permission+0x39f/0x500\n   ? srso_return_thunk+0x5/0x5f\n   ? lock_is_held_type+0x9e/0x120\n   vfs_write+0x98e/0x1000\n   ...\n   \u003c/TASK\u003e\n\nWith this fix applied on top of the same test setup, rerunning the\nreproducer with fail-nth=1 yields no corresponding Oops reports."
    }
  ],
  "id": "CVE-2026-63809",
  "lastModified": "2026-10-19T20:19:21.623",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-63809",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-16T15:31:06.256343Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-19T12:16:53.757",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4c21b5927d4364bfe7365f2700da5fea0ed0d004"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/65bd0c0afb0e1bf3287458e342429b069624f7d4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/70df4de46577fab5e25418f014583155a147c902"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/81fc9a13acae99966232f0e055eb2e445263b89a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/838fe9c28121777c59a9406710a68fcf77bb8017"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ],
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary"
    }
  ]
}



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