CVE-2026-68169 (GCVE-0-2026-68169)
Vulnerability from cvelistv5
Published
2026-08-10 11:59
Modified
2026-08-23 12:46
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: userspace: fix use-after-free in get_local_id In mptcp_pm_userspace_get_local_id(), the address entry is looked up under spinlock, but its id is read after dropping the lock. A concurrent deletion can free the entry between the unlock and the read, leading to UAF. The race window is narrow. It was reproduced only with a locally constructed stress test that repeatedly overlaps an MP_JOIN SYN with a MPTCP_PM_CMD_SUBFLOW_DESTROY request. However, the KASAN report below confirms that the race is reachable: [ 666.319376] BUG: KASAN: slab-use-after-free in mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319386] Read of size 1 at addr ffff888124845610 by task swapper/0/0 ... [ 666.319401] Call Trace: [ 666.319405] <IRQ> [ 666.319408] dump_stack_lvl+0x53/0x70 [ 666.319412] print_address_description.constprop.0+0x2c/0x3b0 [ 666.319418] print_report+0xbe/0x2b0 [ 666.319421] ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319423] kasan_report+0xce/0x100 [ 666.319426] ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319429] mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319433] mptcp_pm_get_local_id+0x371/0x440 ... [ 666.319821] Allocated by task 45539: [ 666.319844] kasan_save_stack+0x33/0x60 [ 666.319855] kasan_save_track+0x14/0x30 [ 666.319858] __kasan_kmalloc+0x8f/0xa0 [ 666.319863] __kmalloc_noprof+0x1e7/0x520 [ 666.319867] sock_kmalloc+0xdf/0x130 [ 666.319885] sock_kmemdup+0x1b/0x40 [ 666.319888] mptcp_userspace_pm_append_new_local_addr+0x261/0x500 [ 666.319910] mptcp_pm_nl_announce_doit+0x16a/0x610 ... [ 666.319967] Freed by task 45560: [ 666.319988] kasan_save_stack+0x33/0x60 [ 666.319991] kasan_save_track+0x14/0x30 [ 666.319994] kasan_save_free_info+0x3b/0x60 [ 666.319998] __kasan_slab_free+0x43/0x70 [ 666.320000] kfree+0x166/0x440 [ 666.320003] sock_kfree_s+0x1d/0x50 [ 666.320007] mptcp_userspace_pm_delete_local_addr.isra.0+0x157/0x200 [ 666.320011] mptcp_pm_nl_subflow_destroy_doit+0x51d/0xea0 Fix by copying the id into a local variable while still holding the lock, and use -1 as a "not found" sentinel.
References
Impacted products
Vendor Product Version
Linux Linux Version: e373bfc8ec3d6496ec7e11dd7f4d087a44b1009a
Version: ed34dfa19ddbd1e4c85a73636f8cba0211025ea4
Version: f012d796a6de662692159c539689e47e662853a8
Version: f012d796a6de662692159c539689e47e662853a8
Version: f012d796a6de662692159c539689e47e662853a8
Version: f012d796a6de662692159c539689e47e662853a8
Version: 005a3ad289eb604216dcaa03646de36cb08624a0
Version: 6.1.79   ≤
Version: 6.6.18   ≤
Version: 6.7.6   ≤
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/mptcp/pm_userspace.c"
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              "version": "6.12.103",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.42",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "negate": false,
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        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: pm: userspace: fix use-after-free in get_local_id\n\nIn mptcp_pm_userspace_get_local_id(), the address entry is looked up under\nspinlock, but its id is read after dropping the lock. A concurrent deletion\ncan free the entry between the unlock and the read, leading to UAF.\n\nThe race window is narrow. It was reproduced only with a locally\nconstructed stress test that repeatedly overlaps an MP_JOIN SYN with a\nMPTCP_PM_CMD_SUBFLOW_DESTROY request.\n\nHowever, the KASAN report below confirms that the race is reachable:\n\n  [  666.319376] BUG: KASAN: slab-use-after-free in mptcp_userspace_pm_get_local_id+0x1dc/0x1f0\n  [  666.319386] Read of size 1 at addr ffff888124845610 by task swapper/0/0\n  ...\n  [  666.319401] Call Trace:\n  [  666.319405]  \u003cIRQ\u003e\n  [  666.319408]  dump_stack_lvl+0x53/0x70\n  [  666.319412]  print_address_description.constprop.0+0x2c/0x3b0\n  [  666.319418]  print_report+0xbe/0x2b0\n  [  666.319421]  ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0\n  [  666.319423]  kasan_report+0xce/0x100\n  [  666.319426]  ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0\n  [  666.319429]  mptcp_userspace_pm_get_local_id+0x1dc/0x1f0\n  [  666.319433]  mptcp_pm_get_local_id+0x371/0x440\n  ...\n  [  666.319821] Allocated by task 45539:\n  [  666.319844]  kasan_save_stack+0x33/0x60\n  [  666.319855]  kasan_save_track+0x14/0x30\n  [  666.319858]  __kasan_kmalloc+0x8f/0xa0\n  [  666.319863]  __kmalloc_noprof+0x1e7/0x520\n  [  666.319867]  sock_kmalloc+0xdf/0x130\n  [  666.319885]  sock_kmemdup+0x1b/0x40\n  [  666.319888]  mptcp_userspace_pm_append_new_local_addr+0x261/0x500\n  [  666.319910]  mptcp_pm_nl_announce_doit+0x16a/0x610\n  ...\n  [  666.319967] Freed by task 45560:\n  [  666.319988]  kasan_save_stack+0x33/0x60\n  [  666.319991]  kasan_save_track+0x14/0x30\n  [  666.319994]  kasan_save_free_info+0x3b/0x60\n  [  666.319998]  __kasan_slab_free+0x43/0x70\n  [  666.320000]  kfree+0x166/0x440\n  [  666.320003]  sock_kfree_s+0x1d/0x50\n  [  666.320007]  mptcp_userspace_pm_delete_local_addr.isra.0+0x157/0x200\n  [  666.320011]  mptcp_pm_nl_subflow_destroy_doit+0x51d/0xea0\n\nFix by copying the id into a local variable while still holding the lock,\nand use -1 as a \"not found\" sentinel."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-23T12:46:03.401Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/8ce48d2879aafc0e7a6f8bfc3613c0ba979ec6f5"
        },
        {
          "url": "https://git.kernel.org/stable/c/d2c3760b45f2f481a4dd4c5adef4a29dfabd948f"
        },
        {
          "url": "https://git.kernel.org/stable/c/31ce5af66891f79998fb2e8b8df08e3c98fd72e3"
        },
        {
          "url": "https://git.kernel.org/stable/c/d64f6c02495f3fad674038cfa7ec049671b59e7b"
        },
        {
          "url": "https://git.kernel.org/stable/c/40dde4b5d98279471a70e5c8bb713182738c00d9"
        },
        {
          "url": "https://git.kernel.org/stable/c/9bc6d5e4ca9f3cbb41d43400b3a31cb0403796c9"
        }
      ],
      "title": "mptcp: pm: userspace: fix use-after-free in get_local_id",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68169",
    "datePublished": "2026-08-10T11:59:38.177Z",
    "dateReserved": "2026-07-30T09:28:09.372Z",
    "dateUpdated": "2026-08-23T12:46:03.401Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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