FKIE_CVE-2026-64542

Vulnerability from fkie_nvd - Published: 2026-07-27 21:17 - Updated: 2026-08-03 10:16
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: ndisc: fix NULL deref in accept_untracked_na() accept_untracked_na() re-fetches the inet6_dev with __in6_dev_get(dev) and dereferences idev->cnf.accept_untracked_na without a NULL check, even though its only caller ndisc_recv_na() already fetched and NULL-checked idev for the same device. Both reads of dev->ip6_ptr run in the same RCU read-side critical section, but a concurrent addrconf_ifdown() can clear dev->ip6_ptr between them: lowering the MTU below IPV6_MIN_MTU calls addrconf_ifdown() without the synchronize_net() that orders the unregister path, so the re-fetch returns NULL and oopses: BUG: KASAN: null-ptr-deref in ndisc_recv_na (net/ipv6/ndisc.c:974) Read of size 4 at addr 0000000000000364 Call Trace: <IRQ> ndisc_recv_na (net/ipv6/ndisc.c:974) icmpv6_rcv (net/ipv6/icmp.c:1193) ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:479) ip6_input_finish (net/ipv6/ip6_input.c:534) ip6_input (net/ipv6/ip6_input.c:545) ip6_mc_input (net/ipv6/ip6_input.c:635) ipv6_rcv (net/ipv6/ip6_input.c:351) </IRQ> It is reachable by an unprivileged user via a network namespace. Pass the caller's already validated idev instead of re-fetching it; the idev stays alive for the whole RCU critical section, so it is safe even after dev->ip6_ptr has been cleared.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/160d3f0d7a556ceae505dcab521a37057b4ce28f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/62c719203cb521b64fab74da94a81bdde5c18808
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/63d1c23764de2309cedbb779c75188d257a09d9b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a6450f7cfae57b382cbaf66a577765c9a88b3c58
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d186e942365acece7c56d39da05dd63bf95b280a
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ndisc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "160d3f0d7a556ceae505dcab521a37057b4ce28f",
              "status": "affected",
              "version": "aaa5f515b16b6b3e137779ffb4c9558bb58c1e75",
              "versionType": "git"
            },
            {
              "lessThan": "62c719203cb521b64fab74da94a81bdde5c18808",
              "status": "affected",
              "version": "aaa5f515b16b6b3e137779ffb4c9558bb58c1e75",
              "versionType": "git"
            },
            {
              "lessThan": "a6450f7cfae57b382cbaf66a577765c9a88b3c58",
              "status": "affected",
              "version": "aaa5f515b16b6b3e137779ffb4c9558bb58c1e75",
              "versionType": "git"
            },
            {
              "lessThan": "63d1c23764de2309cedbb779c75188d257a09d9b",
              "status": "affected",
              "version": "aaa5f515b16b6b3e137779ffb4c9558bb58c1e75",
              "versionType": "git"
            },
            {
              "lessThan": "d186e942365acece7c56d39da05dd63bf95b280a",
              "status": "affected",
              "version": "aaa5f515b16b6b3e137779ffb4c9558bb58c1e75",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ndisc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.0"
            },
            {
              "lessThan": "6.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.97",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.40",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "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\nipv6: ndisc: fix NULL deref in accept_untracked_na()\n\naccept_untracked_na() re-fetches the inet6_dev with __in6_dev_get(dev)\nand dereferences idev-\u003ecnf.accept_untracked_na without a NULL check,\neven though its only caller ndisc_recv_na() already fetched and\nNULL-checked idev for the same device.\n\nBoth reads of dev-\u003eip6_ptr run in the same RCU read-side critical\nsection, but a concurrent addrconf_ifdown() can clear dev-\u003eip6_ptr\nbetween them: lowering the MTU below IPV6_MIN_MTU calls addrconf_ifdown()\nwithout the synchronize_net() that orders the unregister path, so the\nre-fetch returns NULL and oopses:\n\n BUG: KASAN: null-ptr-deref in ndisc_recv_na (net/ipv6/ndisc.c:974)\n Read of size 4 at addr 0000000000000364\n Call Trace:\n  \u003cIRQ\u003e\n  ndisc_recv_na (net/ipv6/ndisc.c:974)\n  icmpv6_rcv (net/ipv6/icmp.c:1193)\n  ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:479)\n  ip6_input_finish (net/ipv6/ip6_input.c:534)\n  ip6_input (net/ipv6/ip6_input.c:545)\n  ip6_mc_input (net/ipv6/ip6_input.c:635)\n  ipv6_rcv (net/ipv6/ip6_input.c:351)\n  \u003c/IRQ\u003e\n\nIt is reachable by an unprivileged user via a network namespace.\n\nPass the caller\u0027s already validated idev instead of re-fetching it; the\nidev stays alive for the whole RCU critical section, so it is safe even\nafter dev-\u003eip6_ptr has been cleared."
    }
  ],
  "id": "CVE-2026-64542",
  "lastModified": "2026-08-03T10:16:32.820",
  "metrics": {},
  "published": "2026-07-27T21:17:06.730",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/160d3f0d7a556ceae505dcab521a37057b4ce28f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/62c719203cb521b64fab74da94a81bdde5c18808"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/63d1c23764de2309cedbb779c75188d257a09d9b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a6450f7cfae57b382cbaf66a577765c9a88b3c58"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d186e942365acece7c56d39da05dd63bf95b280a"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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