CVE-2026-98802 (GCVE-0-2026-98802)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:48 – Updated: 2026-10-19 09:25
VLAI
Title
seg6: ensure packet data is writable before modifying SRH and IPv6 DA
Summary
In the Linux kernel, the following vulnerability has been resolved: seg6: ensure packet data is writable before modifying SRH and IPv6 DA advance_nextseg() modifies the SRH Segments Left field and the IPv6 destination address without ensuring the packet data is writable. seg6_next_csid_advance_arg() has the same problem when it advances the NEXT-C-SID argument in the destination address. The skb may be cloned, for example by an AF_PACKET socket receiving on the ingress device. advance_nextseg() and seg6_next_csid_advance_arg() then write into the packet data shared with the clone. A read from that socket can return the modified packet instead of the received one. The simplified path below shows this for advance_nextseg(): __netif_receive_skb_one_core __netif_receive_skb_core deliver_skb [orig: users=2, cloned=0] packet_rcv skb_clone clone queued to the AF_PACKET socket consume_skb(orig) [orig: users=1, cloned=1] ipv6_rcv ip6_rcv_core skb_share_check: no-op [orig: users=1] [...] input_action_end_core advance_nextseg writes into the data shared with the clone Call skb_ensure_writable() in advance_nextseg() and in seg6_next_csid_advance_arg() before they modify the packet data. skb_ensure_writable() may reallocate skb->head, which invalidates the pointers into the packet data taken before the call. advance_nextseg() now returns a valid SRH pointer, or NULL if skb_ensure_writable() fails. seg6_next_csid_advance_arg() takes the pointer to the destination address from the skb after skb_ensure_writable(). On failure, the callers drop the packet with SKB_DROP_REASON_NOMEM.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7056 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 140f04c33bbcf89440dcaf8bef04918abff5a52d , < e9141fdb7a2ead48cfcd60c681aba91d3014255b (git)
Affected: 140f04c33bbcf89440dcaf8bef04918abff5a52d , < 8ae3f4067ba4ae3a15581392f6dac422e3d3def0 (git)
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Linux Linux Affected: 4.14
Unaffected: 0 , < 4.14 (semver)
Unaffected: 7.2.10 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/seg6_local.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e9141fdb7a2ead48cfcd60c681aba91d3014255b",
              "status": "affected",
              "version": "140f04c33bbcf89440dcaf8bef04918abff5a52d",
              "versionType": "git"
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              "status": "affected",
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          "product": "Linux",
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            "net/ipv6/seg6_local.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "4.14"
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              "version": "0",
              "versionType": "semver"
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              "version": "7.3",
              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.10",
                  "versionStartIncluding": "4.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "4.14",
                  "vulnerable": true
                }
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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\nseg6: ensure packet data is writable before modifying SRH and IPv6 DA\n\nadvance_nextseg() modifies the SRH Segments Left field and the IPv6\ndestination address without ensuring the packet data is writable.\nseg6_next_csid_advance_arg() has the same problem when it advances the\nNEXT-C-SID argument in the destination address.\n\nThe skb may be cloned, for example by an AF_PACKET socket receiving on\nthe ingress device. advance_nextseg() and seg6_next_csid_advance_arg()\nthen write into the packet data shared with the clone. A read from that\nsocket can return the modified packet instead of the received one. The\nsimplified path below shows this for advance_nextseg():\n\n__netif_receive_skb_one_core\n  __netif_receive_skb_core\n    deliver_skb               [orig: users=2, cloned=0]\n      packet_rcv\n        skb_clone             clone queued to the AF_PACKET socket\n        consume_skb(orig)     [orig: users=1, cloned=1]\n  ipv6_rcv\n    ip6_rcv_core              skb_share_check: no-op [orig: users=1]\n    [...]\n      input_action_end_core\n        advance_nextseg       writes into the data shared with the clone\n\nCall skb_ensure_writable() in advance_nextseg() and in\nseg6_next_csid_advance_arg() before they modify the packet data.\nskb_ensure_writable() may reallocate skb-\u003ehead, which invalidates the\npointers into the packet data taken before the call.\nadvance_nextseg() now returns a valid SRH pointer, or NULL if\nskb_ensure_writable() fails.\nseg6_next_csid_advance_arg() takes the pointer to the destination\naddress from the skb after skb_ensure_writable().\nOn failure, the callers drop the packet with SKB_DROP_REASON_NOMEM."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:25:55.677Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e9141fdb7a2ead48cfcd60c681aba91d3014255b"
        },
        {
          "url": "https://git.kernel.org/stable/c/8ae3f4067ba4ae3a15581392f6dac422e3d3def0"
        }
      ],
      "title": "seg6: ensure packet data is writable before modifying SRH and IPv6 DA",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98802",
    "datePublished": "2026-10-18T15:48:49.192Z",
    "dateReserved": "2026-09-25T10:25:14.371Z",
    "dateUpdated": "2026-10-19T09:25:55.677Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-98802",
      "date": "2026-10-25",
      "epss": "0.00155",
      "percentile": "0.04621"
    },
    "microsoft_vex": {
      "current_release_date": "2026-10-21T18:40:43.000Z",
      "cve": "CVE-2026-98802",
      "id": "msrc_CVE-2026-98802",
      "initial_release_date": "2026-10-20T01:10:47.000Z",
      "product_status:known_affected": "1",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "seg6: ensure packet data is writable before modifying SRH and IPv6 DA",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-98802.json",
      "version": "2"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "net/ipv6/seg6_local.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
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            ],
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        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: ensure packet data is writable before modifying SRH and IPv6 DA\n\nadvance_nextseg() modifies the SRH Segments Left field and the IPv6\ndestination address without ensuring the packet data is writable.\nseg6_next_csid_advance_arg() has the same problem when it advances the\nNEXT-C-SID argument in the destination address.\n\nThe skb may be cloned, for example by an AF_PACKET socket receiving on\nthe ingress device. advance_nextseg() and seg6_next_csid_advance_arg()\nthen write into the packet data shared with the clone. A read from that\nsocket can return the modified packet instead of the received one. The\nsimplified path below shows this for advance_nextseg():\n\n__netif_receive_skb_one_core\n  __netif_receive_skb_core\n    deliver_skb               [orig: users=2, cloned=0]\n      packet_rcv\n        skb_clone             clone queued to the AF_PACKET socket\n        consume_skb(orig)     [orig: users=1, cloned=1]\n  ipv6_rcv\n    ip6_rcv_core              skb_share_check: no-op [orig: users=1]\n    [...]\n      input_action_end_core\n        advance_nextseg       writes into the data shared with the clone\n\nCall skb_ensure_writable() in advance_nextseg() and in\nseg6_next_csid_advance_arg() before they modify the packet data.\nskb_ensure_writable() may reallocate skb-\u003ehead, which invalidates the\npointers into the packet data taken before the call.\nadvance_nextseg() now returns a valid SRH pointer, or NULL if\nskb_ensure_writable() fails.\nseg6_next_csid_advance_arg() takes the pointer to the destination\naddress from the skb after skb_ensure_writable().\nOn failure, the callers drop the packet with SKB_DROP_REASON_NOMEM."
          }
        ],
        "id": "CVE-2026-98802",
        "lastModified": "2026-10-19T10:19:44.260",
        "metrics": {},
        "published": "2026-10-18T16:17:34.250",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/8ae3f4067ba4ae3a15581392f6dac422e3d3def0"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
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      "current_release_date": "2026-10-23T15:36:07+00:00",
      "cve": "CVE-2026-98802",
      "id": "CVE-2026-98802",
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      "product_status:known_affected": "187",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: seg6: ensure packet data is writable before modifying SRH and IPv6 DA",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98802.json",
      "version": "3"
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      "current_release_date": "2026-10-22T16:34:21Z",
      "cve": "CVE-2026-98802",
      "id": "CVE-2026-98802",
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      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-98802",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-98802.json",
      "version": "2"
    }
  }
}



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