CVE-2026-98485 (GCVE-0-2026-98485)
Vulnerability from cvelistv5
Published
2026-10-18 15:16
Modified
2026-10-24 14:09
Severity ?
7.1 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: ip6t_rt: fix zero-address non-strict match out-of-bounds read rt_mt6_check() permits rules to be configured with rtinfo->addrnr == 0 even when address matching (IP6T_RT_FST_MASK) is requested. In the IP6T_RT_FST_NSTRICT path, rt_mt6() evaluates packet routing addresses against rtinfo->addrs[i] and terminates backwards at the bottom of the loop: if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) { i++; } if (i == rtinfo->addrnr) break; When addrnr is 0, if the first packet address matches rtinfo->addrs[0], i is incremented to 1. Because i is now strictly greater than addrnr (0), the loop termination condition (i == rtinfo->addrnr) is bypassed and will never be satisfied. If a crafted IPv6 packet contains matching routing addresses, i will advance past IP6T_RT_HOPS (16). The subsequent call to ipv6_addr_equal() reads beyond struct ip6t_rt, triggering UBSAN/KASAN out-of-bounds warnings or kernel panics. Fix this by: 1. Rejecting rules in rt_mt6_check() where IP6T_RT_FST_MASK is set but rtinfo->addrnr is zero. 2. In rt_mt6(), moving the termination condition (i < rtinfo->addrnr) into the for-loop header condition and removing the backwards break at the end of the loop body.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/netfilter/ip6t_rt.c"
          ],
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          "product": "Linux",
          "programFiles": [
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          "vendor": "Linux",
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              "version": "7.3",
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      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ip6t_rt: fix zero-address non-strict match out-of-bounds read\n\nrt_mt6_check() permits rules to be configured with rtinfo-\u003eaddrnr == 0\neven when address matching (IP6T_RT_FST_MASK) is requested.\n\nIn the IP6T_RT_FST_NSTRICT path, rt_mt6() evaluates packet routing\naddresses against rtinfo-\u003eaddrs[i] and terminates backwards at the bottom\nof the loop:\n\n    if (ipv6_addr_equal(ap, \u0026rtinfo-\u003eaddrs[i])) {\n        i++;\n    }\n    if (i == rtinfo-\u003eaddrnr)\n        break;\n\nWhen addrnr is 0, if the first packet address matches rtinfo-\u003eaddrs[0],\ni is incremented to 1. Because i is now strictly greater than addrnr (0),\nthe loop termination condition (i == rtinfo-\u003eaddrnr) is bypassed and will\nnever be satisfied.\n\nIf a crafted IPv6 packet contains matching routing addresses, i will\nadvance past IP6T_RT_HOPS (16). The subsequent call to ipv6_addr_equal()\nreads beyond struct ip6t_rt, triggering UBSAN/KASAN out-of-bounds warnings\nor kernel panics.\n\nFix this by:\n1. Rejecting rules in rt_mt6_check() where IP6T_RT_FST_MASK is set but\n   rtinfo-\u003eaddrnr is zero.\n2. In rt_mt6(), moving the termination condition (i \u003c rtinfo-\u003eaddrnr)\n   into the for-loop header condition and removing the backwards break\n   at the end of the loop body."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bad state enters through local setsockopt(IP6T_SO_SET_REPLACE) or NFT_MSG_NEWRULE rule installation; ip6_rcv then reaches rt_mt6 through NF_INET_PRE_ROUTING and ip6t_do_table. A remote packet alone cannot create the required zero-address rule.\nAC:L - The attacker controls the rule\u0027s addrs[] despite addrnr being zero and can send a 17-address routing header whose first 16 addresses match, making rt_mt6 deterministically read addrs[16]. No race or external timing condition is required.\nPR:L - do_ip6t_set_ctl requires ns_capable(sock_net(sk)-\u003euser_ns, CAP_NET_ADMIN), while nfnetlink uses netlink_net_capable; an unprivileged user can satisfy either check in a user-created user and network namespace.\nUI:N - The attacker installs the malformed rule and injects the triggering IPv6 packet through their own syscalls. No action by another user is needed.\nS:U - The invalid read occurs during netfilter rule evaluation inside the same host kernel security authority. It does not cross a VM, IOMMU, or comparable scope boundary.\nC:H - ipv6_addr_equal() reads 16 bytes from each selected \u0026rtinfo-\u003eaddrs[i], and rt_mt6 can advance beyond the fixed 16-entry array across up to 127 routing-header address iterations. The overread is therefore not strictly bounded to a few bytes.\nI:N - rt_mt6 only fetches the out-of-bounds address for comparison and updates its local index; it performs no out-of-bounds write or other memory modification.\nA:H - At i == 16, the fixed-array subscript and 16-byte ipv6_addr_equal() load trigger UBSAN/KASAN out-of-bounds handling and can panic the kernel, as documented by the fix. The attacker can repeat the rule-and-packet sequence without a race."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:09:02.897Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/959d1829d1ce8b91b435b24a923b51bcc8897090"
        },
        {
          "url": "https://git.kernel.org/stable/c/fe336bab13834394320997de8b16ca4a913b4f13"
        },
        {
          "url": "https://git.kernel.org/stable/c/5a54f8b7f7fe207a5c14713015a5820588faf1ad"
        },
        {
          "url": "https://git.kernel.org/stable/c/b89249819a7d6698bed152feafd3bc6c08489d15"
        },
        {
          "url": "https://git.kernel.org/stable/c/dd55c0ea87bf70e4e4b3b683acd29ef981335b26"
        },
        {
          "url": "https://git.kernel.org/stable/c/191239b0939692e92459d8d32cad14247fa93f89"
        },
        {
          "url": "https://git.kernel.org/stable/c/d9cf4ac6f326330e1fe4d95671d36a6ff3593f64"
        },
        {
          "url": "https://git.kernel.org/stable/c/82313c169eddc02b1bf5ba6b427803e272d3ec42"
        }
      ],
      "title": "netfilter: ip6t_rt: fix zero-address non-strict match out-of-bounds read",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98485",
    "datePublished": "2026-10-18T15:16:00.435Z",
    "dateReserved": "2026-09-25T10:25:14.352Z",
    "dateUpdated": "2026-10-24T14:09:02.897Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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