CVE-2026-89562 (GCVE-0-2026-89562)
Vulnerability from cvelistv5
Published
2026-09-11 19:44
Modified
2026-10-19 08:48
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ip6_gre: fix hardware header length for NBMA tunnels ip6gre_tnl_link_config_route() accumulates the lower device's hardware header length into dev->hard_header_len whenever header_ops is set. This is incorrect for both users of header_ops. ip6gretap and ip6erspan have a fixed Ethernet hardware header length. For an NBMA ip6gre tunnel, ip6gre_header() creates only the GRE header, the optional FOU or GUE header, and the outer IPv6 header. The lower device header is headroom needed later, not part of the tunnel device's hardware header. Keep the lower device header in needed_headroom. Set hard_header_len to the tunnel header length only for ARPHRD_IP6GRE devices with header_ops, and leave the fixed Ethernet header length unchanged for tap and erspan devices.
References
Impacted products
Vendor Product Version
Linux Linux Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: 832ba596494b2c9eac7760259eff2d8b7dcad0ee
Version: cf3d9717a5271573fa193c4dfa0df856295d5b15
Version: 187a6daf5db45adc807c85bbe285319107bed198
Version: d9897bb66ce989325b4bf4cdbb6a799e4ac878b6
Version: 4.19.162   ≤
Version: 5.4.82   ≤
Version: 5.9.13   ≤
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{
  "containers": {
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nip6_gre: fix hardware header length for NBMA tunnels\n\nip6gre_tnl_link_config_route() accumulates the lower device\u0027s hardware\nheader length into dev-\u003ehard_header_len whenever header_ops is set. This\nis incorrect for both users of header_ops.\n\nip6gretap and ip6erspan have a fixed Ethernet hardware header length.\nFor an NBMA ip6gre tunnel, ip6gre_header() creates only the GRE header,\nthe optional FOU or GUE header, and the outer IPv6 header. The lower\ndevice header is headroom needed later, not part of the tunnel device\u0027s\nhardware header.\n\nKeep the lower device header in needed_headroom. Set hard_header_len to\nthe tunnel header length only for ARPHRD_IP6GRE devices with header_ops,\nand leave the fixed Ethernet header length unchanged for tap and erspan\ndevices."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is in ip6gre/ip6gretap/ip6erspan link configuration and local transmit: rtnetlink creates the devices, then sendmsg/forwarding uses the inflated hard_header_len. Incoming GRE receive (gre_rcv) does not perform this accounting, and a remote peer cannot build the stacked topology.\nAC:L - An unprivileged attacker fully controls both sides: creating a stack of ip6gretap/ip6erspan devices so each ip6gre_tnl_link_config_route() copies lower hard_header_len plus t_hlen, then sending packets through that stack. No race or victim-side state is required.\nPR:L - Creating these tunnels needs CAP_NET_ADMIN, but rtnetlink checks it with netlink_ns_capable()/sk_ns_capable() against net-\u003euser_ns, so an unprivileged user obtains it via unshare -Urn without init-namespace root.\nUI:N - The attacker creates the stacked ip6gre devices and generates the traffic that drives IP output and header reservation; no other user or administrator action is required.\nS:U - The resulting skb header-offset wrap corrupts kernel heap in the same OS security authority. This is standard in-kernel privilege escalation, not a VM, IOMMU, or hypervisor boundary crossing.\nC:H - Inflated hard_header_len makes LL_RESERVED_SPACE exceed 16-bit skb offsets; after pskb_expand_head the u16 network_header wraps so flow-dissect/skb_pull read from headroom or unrelated heap, enabling arbitrary disclosure as in CVE-2026-80978.\nI:H - Post-wrap, eth_header/ip6gre_header skb_push and tunnel xmit write outer headers at the corrupted skb-\u003edata, giving an out-of-bounds write into unrelated kernel heap that can be used for control-flow hijacking.\nA:H - Wrapped offsets cause kernel oops/panic (page fault in __skb_flow_dissect, KASAN UAF, or skb_under_panic when unsigned short hard_header_len itself wraps), matching the confirmed crash of the companion tunnel-headroom bug."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:48:55.787Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/cb1afd087aedc90e5274537e4fb9bf3f98e5afdb"
        },
        {
          "url": "https://git.kernel.org/stable/c/7719f6e7ed2ffddc2c3bb61f4467b76d49e0af6a"
        },
        {
          "url": "https://git.kernel.org/stable/c/b1e95e3602d8e112458627f14c6c31c21f2188cb"
        },
        {
          "url": "https://git.kernel.org/stable/c/c3457a5aae5fb43f7023d3f3dc472c2afa22acf0"
        },
        {
          "url": "https://git.kernel.org/stable/c/8bfe746afee38dd6e4348ddcd22d554789dbb9ff"
        },
        {
          "url": "https://git.kernel.org/stable/c/b8282668d8fa7c61b80e8e4890729031c291a16c"
        },
        {
          "url": "https://git.kernel.org/stable/c/565038b0092f65afe384961c0f548d605bf438b9"
        },
        {
          "url": "https://git.kernel.org/stable/c/505b6d296c486ef7d1274f279d4c43a172f63224"
        }
      ],
      "title": "ip6_gre: fix hardware header length for NBMA tunnels",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89562",
    "datePublished": "2026-09-11T19:44:33.576Z",
    "dateReserved": "2026-09-11T19:38:34.725Z",
    "dateUpdated": "2026-10-19T08:48:55.787Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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