batman-adv: reject unrepresentable multicast TVLV offsets

{
  "id": "11416e5b82264d134b5b3e05307cf52999ab1a81fd34032bfd5fdcb20ba9d91c",
  "url": "https://osv.dev/vulnerability/CVE-2026-80839",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "batman-adv: reject unrepresentable multicast TVLV offsets",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: batman-adv: reject unrepresentable multicast TVLV offsets The network and transport header fields in struct sk_buff are 16-bit offsets from skb->head, and U16_MAX is reserved as the unset transport header value. batadv_tvlv_call_handler() sets both fields from a received multicast TVLV without checking whether the TVLV end is representable. If the end offset exceeds the field's range, skb_set_transport_header() truncates it so that the transport header precedes the network header. The negative difference is then returned by skb_network_header_len() as a large u32. batadv_mcast_forw_packet() consequently accepts an oversized multicast tracker and accesses memory beyond the skb data. Add skb_set_transport_header_careful(), an offset-aware counterpart to skb_reset_transport_header_careful(), which validates the final head-relative offset before assigning it. Use the new helper in batadv_tvlv_call_handler() and reject unrepresentable TVLVs before setting the network header.",
    "evidence": "osv:CVE-2026-80839",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.108",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.49",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.13",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.3",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-80839",
      "aliases": [
        "CVE-2026-80839"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "07afe1ba288c04280622fa002ed385f1ac0b6fe6"
                },
                {
                  "fixed": "da1f5aa7ec93f2cc17f5cd30efc54f62af433cf2"
                },
                {
                  "fixed": "916ec741e65af072b98e475feaad98c063da1b7c"
                },
                {
                  "fixed": "1b466746fe109127fd983100a228cdd1f1f6ece2"
                },
                {
                  "fixed": "2b46baa591d0a7c16b62f150917187e70d053be6"
                },
                {
                  "fixed": "f12c2de4f542e3220e17e0606f492110064f04cb"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80839.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.8.0"
                },
                {
                  "fixed": "6.12.108"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.49"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.13"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.2.0"
                },
                {
                  "fixed": "7.2.3"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80839.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:48.893030528Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1b466746fe109127fd983100a228cdd1f1f6ece2",
        "https://git.kernel.org/stable/c/2b46baa591d0a7c16b62f150917187e70d053be6",
        "https://git.kernel.org/stable/c/916ec741e65af072b98e475feaad98c063da1b7c",
        "https://git.kernel.org/stable/c/da1f5aa7ec93f2cc17f5cd30efc54f62af433cf2",
        "https://git.kernel.org/stable/c/f12c2de4f542e3220e17e0606f492110064f04cb",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80839.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-80839",
        "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/2026/80xxx/CVE-2026-80839.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-80839",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 517202,
  "published_at": "2026-09-04T15:54:49.378+00:00"
}