CVE-2026-43249 (GCVE-0-2026-43249)
Vulnerability from cvelistv5
Published
2026-05-06 11:28
Modified
2026-08-05 12:26
Severity ?
8.8 (High) - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: 9p/xen: protect xen_9pfs_front_free against concurrent calls The xenwatch thread can race with other back-end change notifications and call xen_9pfs_front_free() twice, hitting the observed general protection fault due to a double-free. Guard the teardown path so only one caller can release the front-end state at a time, preventing the crash. This is a fix for the following double-free: [ 27.052347] Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI [ 27.052357] CPU: 0 UID: 0 PID: 32 Comm: xenwatch Not tainted 6.18.0-02087-g51ab33fc0a8b-dirty #60 PREEMPT(none) [ 27.052363] RIP: e030:xen_9pfs_front_free+0x1d/0x150 [ 27.052368] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 41 55 41 54 55 48 89 fd 48 c7 c7 48 d0 92 85 53 e8 cb cb 05 00 48 8b 45 08 48 8b 55 00 <48> 3b 28 0f 85 f9 28 35 fe 48 3b 6a 08 0f 85 ef 28 35 fe 48 89 42 [ 27.052377] RSP: e02b:ffffc9004016fdd0 EFLAGS: 00010246 [ 27.052381] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88800d66e400 RCX: 0000000000000000 [ 27.052385] RDX: 6b6b6b6b6b6b6b6b RSI: 0000000000000000 RDI: 0000000000000000 [ 27.052389] RBP: ffff88800a887040 R08: 0000000000000000 R09: 0000000000000000 [ 27.052393] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888009e46b68 [ 27.052397] R13: 0000000000000200 R14: 0000000000000000 R15: ffff88800a887040 [ 27.052404] FS: 0000000000000000(0000) GS:ffff88808ca57000(0000) knlGS:0000000000000000 [ 27.052408] CS: e030 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 27.052412] CR2: 00007f9714004360 CR3: 0000000004834000 CR4: 0000000000050660 [ 27.052418] Call Trace: [ 27.052420] <TASK> [ 27.052422] xen_9pfs_front_changed+0x5d5/0x720 [ 27.052426] ? xenbus_otherend_changed+0x72/0x140 [ 27.052430] ? __pfx_xenwatch_thread+0x10/0x10 [ 27.052434] xenwatch_thread+0x94/0x1c0 [ 27.052438] ? __pfx_autoremove_wake_function+0x10/0x10 [ 27.052442] kthread+0xf8/0x240 [ 27.052445] ? __pfx_kthread+0x10/0x10 [ 27.052449] ? __pfx_kthread+0x10/0x10 [ 27.052452] ret_from_fork+0x16b/0x1a0 [ 27.052456] ? __pfx_kthread+0x10/0x10 [ 27.052459] ret_from_fork_asm+0x1a/0x30 [ 27.052463] </TASK> [ 27.052465] Modules linked in: [ 27.052471] ---[ end trace 0000000000000000 ]---
References
Impacted products
Vendor Product Version
Linux Linux Version: c15fe55d14b3b4ded5af2a3260877460a6ffb8ad
Version: c15fe55d14b3b4ded5af2a3260877460a6ffb8ad
Version: c15fe55d14b3b4ded5af2a3260877460a6ffb8ad
Version: c15fe55d14b3b4ded5af2a3260877460a6ffb8ad
Version: be03c4fe72384366fd4077a70966bd3b8fc49013
Version: 1ab4de11232e83b875b071aa44d1155634ca8a1e
Version: 7cc9dbae8a5f73bd555130384ea256018d28f283
Version: 3e0359f151ac151abe3fa71040e450ed69cb824b
Version: 8d3fc907d060c4fb33203e616a395a22083b6566
Version: 4f0e9244770f5b75a16d8c0929063cd336926764
Version: 5f6a8974e9ef317fe63f88bab1f33070195dd147
Version: 4.14.308   ≤
Version: 4.19.276   ≤
Version: 5.4.235   ≤
Version: 5.10.173   ≤
Version: 5.15.100   ≤
Version: 6.1.18   ≤
Version: 6.2.5   ≤
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p/xen: protect xen_9pfs_front_free against concurrent calls\n\nThe xenwatch thread can race with other back-end change notifications\nand call xen_9pfs_front_free() twice, hitting the observed general\nprotection fault due to a double-free. Guard the teardown path so only\none caller can release the front-end state at a time, preventing the\ncrash.\n\nThis is a fix for the following double-free:\n\n[   27.052347] Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI\n[   27.052357] CPU: 0 UID: 0 PID: 32 Comm: xenwatch Not tainted 6.18.0-02087-g51ab33fc0a8b-dirty #60 PREEMPT(none)\n[   27.052363] RIP: e030:xen_9pfs_front_free+0x1d/0x150\n[   27.052368] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 41 55 41 54 55 48 89 fd 48 c7 c7 48 d0 92 85 53 e8 cb cb 05 00 48 8b 45 08 48 8b 55 00 \u003c48\u003e 3b 28 0f 85 f9 28 35 fe 48 3b 6a 08 0f 85 ef 28 35 fe 48 89 42\n[   27.052377] RSP: e02b:ffffc9004016fdd0 EFLAGS: 00010246\n[   27.052381] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88800d66e400 RCX: 0000000000000000\n[   27.052385] RDX: 6b6b6b6b6b6b6b6b RSI: 0000000000000000 RDI: 0000000000000000\n[   27.052389] RBP: ffff88800a887040 R08: 0000000000000000 R09: 0000000000000000\n[   27.052393] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888009e46b68\n[   27.052397] R13: 0000000000000200 R14: 0000000000000000 R15: ffff88800a887040\n[   27.052404] FS:  0000000000000000(0000) GS:ffff88808ca57000(0000) knlGS:0000000000000000\n[   27.052408] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   27.052412] CR2: 00007f9714004360 CR3: 0000000004834000 CR4: 0000000000050660\n[   27.052418] Call Trace:\n[   27.052420]  \u003cTASK\u003e\n[   27.052422]  xen_9pfs_front_changed+0x5d5/0x720\n[   27.052426]  ? xenbus_otherend_changed+0x72/0x140\n[   27.052430]  ? __pfx_xenwatch_thread+0x10/0x10\n[   27.052434]  xenwatch_thread+0x94/0x1c0\n[   27.052438]  ? __pfx_autoremove_wake_function+0x10/0x10\n[   27.052442]  kthread+0xf8/0x240\n[   27.052445]  ? __pfx_kthread+0x10/0x10\n[   27.052449]  ? __pfx_kthread+0x10/0x10\n[   27.052452]  ret_from_fork+0x16b/0x1a0\n[   27.052456]  ? __pfx_kthread+0x10/0x10\n[   27.052459]  ret_from_fork_asm+0x1a/0x30\n[   27.052463]  \u003c/TASK\u003e\n[   27.052465] Modules linked in:\n[   27.052471] ---[ end trace 0000000000000000 ]---"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:A - The vulnerable 9p Xen frontend is reached through Xenbus/backend state changes from a paired Xen backend or service domain on the same host/logical I/O fabric. It is not directly routable over IP, but it is reachable across an adjacent inter-domain channel.\nAC:L - A malicious backend can repeatedly queue the state transitions/removal paths that lead to concurrent or repeated xen_9pfs_front_free() calls. The trigger does not depend on conditions outside the attacker-controlled backend notification sequence.\nPR:N - No privileges in the vulnerable guest are required; the guest frontend accepts the triggering state changes from its configured backend via Xenstore. Control of the backend is the attack position rather than a credential inside the target Linux kernel.\nUI:N - No victim user action is needed after the Xen 9pfs frontend device is present and bound. Backend state changes are processed asynchronously by xenwatch.\nS:U - The corrupted objects and resulting crash/code-execution risk are within the same guest Linux kernel running the vulnerable frontend. The issue does not demonstrate a guest-to-host or hypervisor escape.\nC:H - This is kernel heap memory corruption via double-free of frontend state and associated ring resources. Such corruption can plausibly be shaped into use-after-free/freelist manipulation and arbitrary kernel memory disclosure, so the higher impact is warranted.\nI:H - The double-free can corrupt kernel allocator metadata or free a reallocated object, giving a plausible path to arbitrary write or control-flow compromise. Under the required uncertainty rule, this is scored as high integrity impact.\nA:H - The reported failure is a general protection fault in xenwatch from dereferencing poisoned freed memory. A malicious backend can crash the guest kernel, causing high availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:26:52.660Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a5d00dff97118a32fcf5fec7a4c3f864c4620c4e"
        },
        {
          "url": "https://git.kernel.org/stable/c/59e7707492576bdbfa8c1dbe7d90791df31e4773"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf841d43f7a33d75675ba7f4e214ac1c67913065"
        },
        {
          "url": "https://git.kernel.org/stable/c/ce8ded2e61f47747e31eeefb44dc24a2160a7e32"
        }
      ],
      "title": "9p/xen: protect xen_9pfs_front_free against concurrent calls",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43249",
    "datePublished": "2026-05-06T11:28:40.290Z",
    "dateReserved": "2026-05-01T14:12:55.996Z",
    "dateUpdated": "2026-08-05T12:26:52.660Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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