CVE-2026-89561 (GCVE-0-2026-89561)
Vulnerability from cvelistv5
Published
2026-09-11 19:44
Modified
2026-10-21 12:47
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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: <IRQ> 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 </IRQ> 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 in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths.
References
Impacted products
Vendor Product Version
Linux Linux Version: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3
Version: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3
Version: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3
Version: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3
Version: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/exthdrs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/exthdrs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.7"
            },
            {
              "lessThan": "5.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.160",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.111",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionEndExcluding": "7.3",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()\n\nipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL\ncheck when reading idev-\u003ecnf.rpl_seg_enabled.\n\nWhen the device\u0027s MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears\ndev-\u003eip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev\ncheck in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with\ndev-\u003eip6_ptr already NULL.\n\nReproduced by flooding the receiving interface with ping6 traffic while\nflapping its MTU between 1500 and 1200:\n\n BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070\n Read of size 4 at addr 00000000000006b4 by task ping6/394\n\n CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full)\n Call Trace:\n  \u003cIRQ\u003e\n  kasan_report+0xc6/0x100\n  ipv6_rpl_srh_rcv+0xb3/0x1070\n  ip6_protocol_deliver_rcu+0x759/0x9a0\n  ip6_input_finish+0xa8/0x1b0\n  ip6_input+0xe1/0x490\n  ipv6_rcv+0x33d/0x460\n  __netif_receive_skb_one_core+0xd6/0x130\n  process_backlog+0x2cc/0xa00\n  __napi_poll.constprop.0+0x56/0x270\n  net_rx_action+0x327/0x730\n  handle_softirqs+0x11e/0x630\n  do_softirq+0xb3/0xf0\n  \u003c/IRQ\u003e\n\nBoth ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from\nipv6_rthdr_rcv(), which already has an idev lookup.\n\nFix the NULL dereference on the RPL path by checking idev in\nipv6_rthdr_rcv(), before it calls either function. The callees take idev as\nan argument and no longer call __in6_dev_get(), so the packet is now\ndropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ipv6_rpl_srh_rcv() runs on the IPv6 local-delivery path (ipv6_rcv \u2192 ip6_protocol_deliver_rcu \u2192 ipv6_rthdr_rcv) for any unicast packet with Routing Header type 3; a remote attacker can deliver such packets over the network with no local access.\nAC:L - The attacker drives both sides of the race by flooding type-3 routing-header packets while concurrently dropping the ingress MTU below IPV6_MIN_MTU or deleting the netdev, and the window is large because ip6_rcv_core() drops RCU before extension-header processing.\nPR:N - Sending an unauthenticated IPv6 packet with a type-3 routing header requires no credentials; the NULL deref occurs before the rpl_seg_enabled check, and ip6_ptr teardown also occurs during ordinary container/veth lifecycle on shared hosts.\nUI:N - Exploitation needs only delivery of IPv6 routing-header packets during concurrent interface MTU/teardown; no victim action such as opening a file, mounting a filesystem, or clicking a link is required.\nS:U - A successful trigger oopses the same host kernel that processes the packet and does not cross a VM, hypervisor, IOMMU, or other security-authority boundary.\nC:N - The fault is a pure NULL pointer read of idev-\u003ecnf.rpl_seg_enabled at a fixed offset, causing an immediate page fault with no use-after-free, out-of-bounds read, or other information-disclosure primitive.\nI:N - This is a read-side NULL dereference only; there is no memory write, type confusion, or control-flow hijack primitive beyond crashing the kernel.\nA:H - The NULL dereference occurs in softirq context during IPv6 receive and produces a kernel oops or panic, as shown by the KASAN report in ipv6_rpl_srh_rcv, fully denying availability on the affected system."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:47:51.427Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/62b63a505c10e8db76017ef73c0b243e0dc5d288"
        },
        {
          "url": "https://git.kernel.org/stable/c/e7123e10c86eb88eaa90537dd1f232706de2d308"
        },
        {
          "url": "https://git.kernel.org/stable/c/63f50e9f90d0287ad66a0955ebfc2d3a9c044a1c"
        },
        {
          "url": "https://git.kernel.org/stable/c/eab3a917cdcb182542a3aac6a0d2d30659ca9821"
        },
        {
          "url": "https://git.kernel.org/stable/c/f826df95332c07380206dbd54178b6eefb311aba"
        }
      ],
      "title": "ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89561",
    "datePublished": "2026-09-11T19:44:32.822Z",
    "dateReserved": "2026-09-11T19:38:34.725Z",
    "dateUpdated": "2026-10-21T12:47:51.427Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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