CVE-2026-72429 (GCVE-0-2026-72429)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:44
VLAI
Title
ipv6: ioam: fix type confusion of dst_entry
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: ioam: fix type confusion of dst_entry IOAM uses a dummy dst_entry(null_dst) to mark that the destination should not be changed after the transformation. This dst is stored in the IOAM lwt state and may be passed to dst_cache_set_ip6(). However, the IPv6 dst cache path eventually calls rt6_get_cookie(), which treats the dst_entry as part of a struct rt6_info. Since the null_dst was embedded directly as a struct dst_entry in struct ioam6_lwt, this resulted in an invalid cast and rt6_get_cookie() reading fields from the wrong object. In practice, the wrong cookie is not used while dst->obsolete is zero, but rt6_get_cookie() may also access per-cpu value when rt->sernum is zero. In this case, rt->sernum aliases ioam6_lwt::cache::reset_ts, which can become zero, making this a potential invalid pointer access. Fix this by embedding a full struct rt6_info for the dummy IPv6 route and passing its dst member to the dst APIs.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 47ce7c854563fe8450e9cb8dcd62c6470e28076b , < ea24f911ead85ba3d570a31e37c52b6c949f6928 (git)
Affected: 47ce7c854563fe8450e9cb8dcd62c6470e28076b , < 5a3b2ee1e96d0580a8ed8deda6dfa430604f9ab0 (git)
Affected: 47ce7c854563fe8450e9cb8dcd62c6470e28076b , < 9ed19e11d2146076d117d51a940643990118449b (git)
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Linux Linux Affected: 6.16
Unaffected: 0 , < 6.16 (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "net/ipv6/ioam6_iptunnel.c"
          ],
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          "vendor": "Linux",
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: ioam: fix type confusion of dst_entry\n\nIOAM uses a dummy dst_entry(null_dst) to mark that the destination should\nnot be changed after the transformation. This dst is stored in the IOAM lwt\nstate and may be passed to dst_cache_set_ip6().\n\nHowever, the IPv6 dst cache path eventually calls rt6_get_cookie(), which\ntreats the dst_entry as part of a struct rt6_info. Since the null_dst was\nembedded directly as a struct dst_entry in struct ioam6_lwt, this resulted\nin an invalid cast and rt6_get_cookie() reading fields from the wrong\nobject.\n\nIn practice, the wrong cookie is not used while dst-\u003eobsolete is zero, but\nrt6_get_cookie() may also access per-cpu value when rt-\u003esernum is\nzero. In this case, rt-\u003esernum aliases ioam6_lwt::cache::reset_ts, which\ncan become zero, making this a potential invalid pointer access.\n\nFix this by embedding a full struct rt6_info for the dummy IPv6 route and\npassing its dst member to the dst APIs."
        }
      ],
      "metrics": [
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The flaw is in ioam6_output() on the IPv6 transmit path (lwtunnel_output\u2192dst_output), reachable when remotely sourced IPv6 packets are forwarded or locally output through an IOAM6 LWT route on internet-facing or LAN routers.\nAC:L - Once IOAM6 LWT inline routes exist, an attacker can reliably trigger the null_dst dst_cache_set_ip6() path by sending IPv6 traffic that misses the per-CPU dst cache, without races or uncontrollable memory layout.\nPR:N - Exploitation requires only the ability to send IPv6 packets; IOAM6 LWT route and namespace setup needs CAP_NET_ADMIN on the victim but is an operator deployment prerequisite, not attacker privilege.\nUI:N - No victim user action is required beyond normal network operation; crafted or high-volume IPv6 packets alone drive the vulnerable output path.\nS:U - Impact is kernel memory corruption and crash within the host kernel; it does not cross VM, container, or IOMMU security boundaries.\nC:H - Type confusion makes rt6_get_cookie() treat ioam6_lwt fields as rt6_info members and chase a misinterpreted fib6_info pointer via fib6_get_cookie_safe(), enabling out-of-bounds kernel memory reads.\nI:H - Casting a standalone dst_entry to rt6_info is type confusion that corrupts pointer interpretation and dst_cache cookie state, a class exploitable toward arbitrary kernel writes or control-flow hijack.\nA:H - The confused rt6_info layout can dereference invalid fib6_info/fib6_node pointers, causing kernel oops or panic; memory corruption in the networking fast path also risks host-wide denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:44:08.737Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ea24f911ead85ba3d570a31e37c52b6c949f6928"
        },
        {
          "url": "https://git.kernel.org/stable/c/5a3b2ee1e96d0580a8ed8deda6dfa430604f9ab0"
        },
        {
          "url": "https://git.kernel.org/stable/c/9ed19e11d2146076d117d51a940643990118449b"
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      ],
      "title": "ipv6: ioam: fix type confusion of dst_entry",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72429",
    "datePublished": "2026-08-15T05:56:45.530Z",
    "dateReserved": "2026-08-09T03:40:39.928Z",
    "dateUpdated": "2026-08-17T05:44:08.737Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
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      "date": "2026-09-01",
      "epss": "0.00605",
      "percentile": "0.46591"
    },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-19T17:41:56+00:00",
      "cve": "CVE-2026-72429",
      "id": "CVE-2026-72429",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ipv6: ioam: fix type confusion of dst_entry",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72429.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.