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GHSA-C37C-FRR8-RX54

Vulnerability from github – Published: 2026-07-27 21:31 – Updated: 2026-09-08 09:35
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().

fib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and dereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown() clears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has released tb6_lock, so the RA-driven MTU walk can observe a NULL idev and oops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(), but this re-fetch is unguarded; nexthop-backed routes survive addrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is nulled.

Return 0 when idev is NULL, matching rt6_mtu_change_route() and the fib6_mtu() fix in commit 5ad509c1fdad ("ipv6: Fix null-ptr-deref in fib6_mtu().").

Oops: general protection fault, ... KASAN: null-ptr-deref in range [0x00000000000002a8-0x00000000000002af] RIP: 0010:fib6_nh_mtu_change+0x203/0x990 rt6_mtu_change_route+0x141/0x1d0 __fib6_clean_all+0xd0/0x160 rt6_mtu_change+0xb4/0x100 ndisc_router_discovery+0x24b5/0x2cb0 icmpv6_rcv+0x12e9/0x1710 ipv6_rcv+0x39b/0x410

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64538"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-27T21:17:06Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change().\n\nfib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg-\u003edev) and\ndereferences idev-\u003ecnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev-\u003eip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has\nreleased tb6_lock, so the RA-driven MTU walk can observe a NULL idev and\noops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\nbut this re-fetch is unguarded; nexthop-backed routes survive\naddrconf_ifdown()\u0027s flush, so the walk still reaches it after ip6_ptr is\nnulled.\n\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\nfib6_mtu() fix in commit 5ad509c1fdad (\"ipv6: Fix null-ptr-deref in\nfib6_mtu().\").\n\n  Oops: general protection fault, ... KASAN: null-ptr-deref in range\n        [0x00000000000002a8-0x00000000000002af]\n  RIP: 0010:fib6_nh_mtu_change+0x203/0x990\n   rt6_mtu_change_route+0x141/0x1d0\n   __fib6_clean_all+0xd0/0x160\n   rt6_mtu_change+0xb4/0x100\n   ndisc_router_discovery+0x24b5/0x2cb0\n   icmpv6_rcv+0x12e9/0x1710\n   ipv6_rcv+0x39b/0x410",
  "id": "GHSA-c37c-frr8-rx54",
  "modified": "2026-09-08T09:35:36Z",
  "published": "2026-07-27T21:31:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64538"
    },
    {
      "type": "WEB",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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