FKIE_CVE-2026-80976

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-10-19 09:17
Severity
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: seg6: reset IP6CB after IPv6 decapsulation decap_and_validate() pulls the outer SRv6 headers and makes the inner packet the skb network header. The IPv6 control block still contains values collected while parsing the outer packet, including nhoff and extension-header flags. End.DX6 and End.DT6 route the inner IPv6 packet directly to the IPv6 input path. An unprivileged user can reach End.DT6 from a user and net namespace by installing a local SID and injecting an outer packet with Hop-by-Hop and Destination Options headers followed by an SRH and a minimal inner IPv6 packet. The outer extension headers leave a large nhoff in IP6CB. After decapsulation, ip6_protocol_deliver_rcu() uses that stale offset on the inner packet and reads beyond the skb head. KASAN reports: BUG: KASAN: slab-out-of-bounds in ip6_protocol_deliver_rcu ip6_protocol_deliver_rcu+0x1118/0x1450 ip6_input_finish+0x11b/0x240 seg6_local_input_core+0xed/0x2e0 lwtunnel_input+0x1e9/0x4e0 ipv6_rthdr_rcv+0x525f/0x6c50 ip6_protocol_deliver_rcu+0xcb7/0x1450 Before clearing IP6CB for an inner IPv6 packet, save its incoming interface index and L3 slave state. Restore both after the clear and set nhoff to the inner IPv6 base-header nexthdr field. Use IP6CB(skb)->iif rather than skb->skb_iif because VRF processing can replace skb_iif with the L3 master while IP6CB keeps the receiving interface. Preserve IP6SKB_L3SLAVE for the same reason.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2b154e96fcb3f01fd42765c64e0a56820fbc16eb
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/96c74420ac92930a7e0f21770818544eee4a93d7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9ae92198c24d7dacd4070e2f34f6e1ed3a63061c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a0e2b0a3718f0cf9fb0ee41710b4a6348a7315c8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c73fb911e02b9a766c950bc9707f3e3a96ffd702
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cfa186a0857a0f831dfca67b16bbc40ecfdf3280
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d1f0d353358987ca87f21d8956e2d2854951130d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f967455fb2a5a2079b9eb5823e9ccf359174bf9f
Impacted products
Vendor Product Version
To clipboard 

{
  "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",
          "versions": [
            {
              "lessThan": "d1f0d353358987ca87f21d8956e2d2854951130d",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            },
            {
              "lessThan": "a0e2b0a3718f0cf9fb0ee41710b4a6348a7315c8",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            },
            {
              "lessThan": "9ae92198c24d7dacd4070e2f34f6e1ed3a63061c",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            },
            {
              "lessThan": "96c74420ac92930a7e0f21770818544eee4a93d7",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            },
            {
              "lessThan": "2b154e96fcb3f01fd42765c64e0a56820fbc16eb",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            },
            {
              "lessThan": "cfa186a0857a0f831dfca67b16bbc40ecfdf3280",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            },
            {
              "lessThan": "c73fb911e02b9a766c950bc9707f3e3a96ffd702",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            },
            {
              "lessThan": "f967455fb2a5a2079b9eb5823e9ccf359174bf9f",
              "status": "affected",
              "version": "d7a669dd2f8ba07a17423f4ad586dfc0379882f7",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/seg6_local.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.14"
            },
            {
              "lessThan": "4.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "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"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: reset IP6CB after IPv6 decapsulation\n\ndecap_and_validate() pulls the outer SRv6 headers and makes the inner\npacket the skb network header. The IPv6 control block still contains\nvalues collected while parsing the outer packet, including nhoff and\nextension-header flags.\n\nEnd.DX6 and End.DT6 route the inner IPv6 packet directly to the IPv6\ninput path. An unprivileged user can reach End.DT6 from a user and net\nnamespace by installing a local SID and injecting an outer packet with\nHop-by-Hop and Destination Options headers followed by an SRH and a\nminimal inner IPv6 packet.\n\nThe outer extension headers leave a large nhoff in IP6CB. After\ndecapsulation, ip6_protocol_deliver_rcu() uses that stale offset on the\ninner packet and reads beyond the skb head. KASAN reports:\n\n  BUG: KASAN: slab-out-of-bounds in ip6_protocol_deliver_rcu\n  ip6_protocol_deliver_rcu+0x1118/0x1450\n  ip6_input_finish+0x11b/0x240\n  seg6_local_input_core+0xed/0x2e0\n  lwtunnel_input+0x1e9/0x4e0\n  ipv6_rthdr_rcv+0x525f/0x6c50\n  ip6_protocol_deliver_rcu+0xcb7/0x1450\n\nBefore clearing IP6CB for an inner IPv6 packet, save its incoming\ninterface index and L3 slave state. Restore both after the clear and set\nnhoff to the inner IPv6 base-header nexthdr field.\n\nUse IP6CB(skb)-\u003eiif rather than skb-\u003eskb_iif because VRF processing can\nreplace skb_iif with the L3 master while IP6CB keeps the receiving\ninterface. Preserve IP6SKB_L3SLAVE for the same reason."
    }
  ],
  "id": "CVE-2026-80976",
  "lastModified": "2026-10-19T09:17:29.663",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:19:03.887",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2b154e96fcb3f01fd42765c64e0a56820fbc16eb"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/96c74420ac92930a7e0f21770818544eee4a93d7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9ae92198c24d7dacd4070e2f34f6e1ed3a63061c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a0e2b0a3718f0cf9fb0ee41710b4a6348a7315c8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c73fb911e02b9a766c950bc9707f3e3a96ffd702"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/cfa186a0857a0f831dfca67b16bbc40ecfdf3280"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d1f0d353358987ca87f21d8956e2d2854951130d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f967455fb2a5a2079b9eb5823e9ccf359174bf9f"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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