ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()

{
  "id": "7a89e6a95d55b0367e8ff8e5eb269dc0b2889076e7a2f88f97eae06faade078b",
  "url": "https://osv.dev/vulnerability/CVE-2026-89561",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv() ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL check when reading idev->cnf.rpl_seg_enabled. When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with dev->ip6_ptr already NULL. Reproduced by flooding the receiving interface with ping6 traffic while flapping its MTU between 1500 and 1200: BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070 Read of size 4 at addr 00000000000006b4 by task ping6/394 CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full) Call Trace: kasan_report+0xc6/0x100 ipv6_rpl_srh_rcv+0xb3/0x1070 ip6_protocol_deliver_rcu+0x759/0x9a0 ip6_input_finish+0xa8/0x1b0 ip6_input+0xe1/0x490 ipv6_rcv+0x33d/0x460 __netif_receive_skb_one_core+0xd6/0x130 process_backlog+0x2cc/0xa00 __napi_poll.constprop.0+0x56/0x270 net_rx_action+0x327/0x730 handle_softirqs+0x11e/0x630 do_softirq+0xb3/0xf0 Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from ipv6_rthdr_rcv(), which already has an idev lookup. Fix the NULL dereference on the RPL path by checking idev in ipv6_rthdr_rcv(), before it calls either function. The callees take idev as an argument and no longer call __in6_dev_get(), so the packet is now dropped",
    "evidence": "osv:CVE-2026-89561",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.191",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.111",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.50",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-89561",
      "aliases": [
        "CVE-2026-89561"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                },
                {
                  "fixed": "f5e89dfc0a815c6ed12791d8deb3b6f39dd0621e"
                },
                {
                  "fixed": "62b63a505c10e8db76017ef73c0b243e0dc5d288"
                },
                {
                  "fixed": "e7123e10c86eb88eaa90537dd1f232706de2d308"
                },
                {
                  "fixed": "63f50e9f90d0287ad66a0955ebfc2d3a9c044a1c"
                },
                {
                  "fixed": "eab3a917cdcb182542a3aac6a0d2d30659ca9821"
                },
                {
                  "fixed": "f826df95332c07380206dbd54178b6eefb311aba"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89561.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.7.0"
                },
                {
                  "fixed": "6.1.191"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
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                }
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            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.50"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89561.json"
          }
        }
      ],
      "modified": "2026-11-01T02:30:47.559507648Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/62b63a505c10e8db76017ef73c0b243e0dc5d288",
        "https://git.kernel.org/stable/c/63f50e9f90d0287ad66a0955ebfc2d3a9c044a1c",
        "https://git.kernel.org/stable/c/e7123e10c86eb88eaa90537dd1f232706de2d308",
        "https://git.kernel.org/stable/c/eab3a917cdcb182542a3aac6a0d2d30659ca9821",
        "https://git.kernel.org/stable/c/f5e89dfc0a815c6ed12791d8deb3b6f39dd0621e",
        "https://git.kernel.org/stable/c/f826df95332c07380206dbd54178b6eefb311aba",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89561.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89561",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89561.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89561",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518614,
  "published_at": "2026-09-11T19:44:32.822+00:00"
}