{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2023-53821",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2023-53821"
  ],
  "published": "2025-12-09T01:31:24Z",
  "summary": "ip6_vti: fix slab-use-after-free in decode_session6",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nip6_vti: fix slab-use-after-free in decode_session6\n\nWhen ipv6_vti device is set to the qdisc of the sfb type, the cb field\nof the sent skb may be modified during enqueuing. Then,\nslab-use-after-free may occur when ipv6_vti device sends IPv6 packets.\n\nThe stack information is as follows:\nBUG: KASAN: slab-use-after-free in decode_session6+0x103f/0x1890\nRead of size 1 at addr ffff88802e08edc2 by task swapper/0/0\nCPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0-next-20230707-00001-g84e2cad7f979 #410\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014\nCall Trace:\n<IRQ>\ndump_stack_lvl+0xd9/0x150\nprint_address_description.constprop.0+0x2c/0x3c0\nkasan_report+0x11d/0x130\ndecode_session6+0x103f/0x1890\n__xfrm_decode_session+0x54/0xb0\nvti6_tnl_xmit+0x3e6/0x1ee0\ndev_hard_start_xmit+0x187/0x700\nsch_direct_xmit+0x1a3/0xc30\n__qdisc_run+0x510/0x17a0\n__dev_queue_xmit+0x2215/0x3b10\nneigh_connected_output+0x3c2/0x550\nip6_finish_output2+0x55a/0x1550\nip6_finish_output+0x6b9/0x1270\nip6_output+0x1f1/0x540\nndisc_send_skb+0xa63/0x1890\nndisc_send_rs+0x132/0x6f0\naddrconf_rs_timer+0x3f1/0x870\ncall_timer_fn+0x1a0/0x580\nexpire_timers+0x29b/0x4b0\nrun_timer_softirq+0x326/0x910\n__do_softirq+0x1d4/0x905\nirq_exit_rcu+0xb7/0x120\nsysvec_apic_timer_interrupt+0x97/0xc0\n</IRQ>\nAllocated by task 9176:\nkasan_save_stack+0x22/0x40\nkasan_set_track+0x25/0x30\n__kasan_slab_alloc+0x7f/0x90\nkmem_cache_alloc_node+0x1cd/0x410\nkmalloc_reserve+0x165/0x270\n__alloc_skb+0x129/0x330\nnetlink_sendmsg+0x9b1/0xe30\nsock_sendmsg+0xde/0x190\n____sys_sendmsg+0x739/0x920\n___sys_sendmsg+0x110/0x1b0\n__sys_sendmsg+0xf7/0x1c0\ndo_syscall_64+0x39/0xb0\nentry_SYSCALL_64_after_hwframe+0x63/0xcd\nFreed by task 9176:\nkasan_save_stack+0x22/0x40\nkasan_set_track+0x25/0x30\nkasan_save_free_info+0x2b/0x40\n____kasan_slab_free+0x160/0x1c0\nslab_free_freelist_hook+0x11b/0x220\nkmem_cache_free+0xf0/0x490\nskb_free_head+0x17f/0x1b0\nskb_release_data+0x59c/0x850\nconsume_skb+0xd2/0x170\nnetlink_unicast+0x54f/0x7f0\nnetlink_sendmsg+0x926/0xe30\nsock_sendmsg+0xde/0x190\n____sys_sendmsg+0x739/0x920\n___sys_sendmsg+0x110/0x1b0\n__sys_sendmsg+0xf7/0x1c0\ndo_syscall_64+0x39/0xb0\nentry_SYSCALL_64_after_hwframe+0x63/0xcd\nThe buggy address belongs to the object at ffff88802e08ed00\nwhich belongs to the cache skbuff_small_head of size 640\nThe buggy address is located 194 bytes inside of\nfreed 640-byte region [ffff88802e08ed00, ffff88802e08ef80)\n\nAs commit f855691975bb (\"xfrm6: Fix the nexthdr offset in\n_decode_session6.\") showed, xfrm_decode_session was originally intended\nonly for the receive path. IP6CB(skb)->nhoff is not set during\ntransmission. Therefore, set the cb field in the skb to 0 before\nsending packets.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.21-1+rpt1"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v6",
            "binary_version": "1:6.1.21-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v7",
            "binary_version": "1:6.1.21-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v7l",
            "binary_version": "1:6.1.21-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v8",
            "binary_version": "1:6.1.21-1+rpt1"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.21-1+rpt1": {
            "linux_commit": "0afb5e98488aed7017b9bf321b575d0177feb7ed",
            "upstream_version": "6.1.21",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.47"
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2023-53821"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0f0ab8d52ee0062b28367dea23c29e254a26d7db"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/fa6c6c04f6c9b21b315023f487e5a07ae7fcf647"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/eb47e612e59c358c3968a92f90dd36c78c9a2106"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ec23b25e5687dbd644c0f57bcb6af22dd5a6dd36"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a1639a82ce14af76b6419778d343ccbff86ee626"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/55ad2309205cc00c585344374c7472420e1b2c12"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c070688bfbe7759e61e697e421b2a331b0dd74bc"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/9fd41f1ba638938c9a1195d09bc6fa3be2712f25"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-05-12T04:54:46Z"
  }
}