CVE-2026-97612 (GCVE-0-2026-97612)
Vulnerability from cvelistv5
Published
2026-09-25 10:22
Modified
2026-10-19 09:10
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: net: mpls: clear inner_protocol when the last label is popped skb_mpls_push() records the pre-encapsulation network header once, gated on !skb->inner_protocol. skb_mpls_pop() never clears that record, so it outlives the encapsulation it describes. Open vSwitch can then re-push MPLS onto a packet whose inner_network_header still points at the older, deeper offset: push a label, pop every label, recirculate (ovs_flow_key_update() re-derives key->eth.type and resets network_header, but leaves inner_*), then push again. ovs_fragment() trusts the record: skb->network_header = skb->inner_network_header; so skb_network_offset() goes negative. The bound check is signed: if (skb_network_offset(skb) > MAX_L2_LEN) a negative offset passes it, and prepare_frag() widens the value: unsigned int hlen = skb_network_offset(skb); memcpy(&data->l2_data, skb->data, hlen); which is a ~4GiB memcpy out of a 30-byte per-CPU buffer. Reproduced on v7.3-rc1. RDX is the truncated length, (unsigned int)(-8): BUG: unable to handle page fault for address: ffffe8ffffc16000 #PF: supervisor write access in kernel mode Oops: 0002 [#1] SMP KASAN NOPTI RIP: 0010:memcpy+0x8/0x20 RDX: 00000000fffffff8 RSI: ffff888105d732db RDI: ffffe8ffffc16000 prepare_frag+0x3df/0x4e0 ovs_fragment+0x589/0x7e0 do_output+0x4ce/0x5e0 do_execute_actions+0x55d2/0x7b30 ovs_execute_actions+0xea/0x450 Same root-cause shape as commit 975b5b067f52 ("ipv6: sr: restore network header before routing and forwarding"): a stale network header offset reaching a consumer that widens it. Here it originates in the MPLS push/pop path. Clear inner_protocol once the packet is no longer MPLS, so a later push re-records the current header. net/sched/act_mpls.c is the only other skb_mpls_pop() caller and gets the same fix; sch_frag.c saves and restores inner_protocol around fragmentation in the same way OVS does.
References
Impacted products
Vendor Product Version
Linux Linux Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
Version: 48d2ab609b6bbecb7698487c8579bc40de9d6dfa
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/skbuff.c"
          ],
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "version": "5.10.271",
              "versionType": "semver"
            },
            {
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              "version": "5.15.222",
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            },
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              "version": "6.1.189",
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              "version": "6.6.158",
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              "version": "6.12.111",
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              "version": "6.18.53",
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              "version": "7.2.7",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.271",
                  "versionStartIncluding": "4.9",
                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mpls: clear inner_protocol when the last label is popped\n\nskb_mpls_push() records the pre-encapsulation network header once, gated\non !skb-\u003einner_protocol. skb_mpls_pop() never clears that record, so it\noutlives the encapsulation it describes.\n\nOpen vSwitch can then re-push MPLS onto a packet whose\ninner_network_header still points at the older, deeper offset: push a\nlabel, pop every label, recirculate (ovs_flow_key_update() re-derives\nkey-\u003eeth.type and resets network_header, but leaves inner_*), then push\nagain. ovs_fragment() trusts the record:\n\n\tskb-\u003enetwork_header = skb-\u003einner_network_header;\n\nso skb_network_offset() goes negative. The bound check is signed:\n\n\tif (skb_network_offset(skb) \u003e MAX_L2_LEN)\n\na negative offset passes it, and prepare_frag() widens the value:\n\n\tunsigned int hlen = skb_network_offset(skb);\n\tmemcpy(\u0026data-\u003el2_data, skb-\u003edata, hlen);\n\nwhich is a ~4GiB memcpy out of a 30-byte per-CPU buffer.\n\nReproduced on v7.3-rc1. RDX is the truncated length, (unsigned int)(-8):\n\n  BUG: unable to handle page fault for address: ffffe8ffffc16000\n  #PF: supervisor write access in kernel mode\n  Oops: 0002 [#1] SMP KASAN NOPTI\n  RIP: 0010:memcpy+0x8/0x20\n  RDX: 00000000fffffff8 RSI: ffff888105d732db RDI: ffffe8ffffc16000\n   prepare_frag+0x3df/0x4e0\n   ovs_fragment+0x589/0x7e0\n   do_output+0x4ce/0x5e0\n   do_execute_actions+0x55d2/0x7b30\n   ovs_execute_actions+0xea/0x450\n\nSame root-cause shape as commit 975b5b067f52 (\"ipv6: sr: restore network\nheader before routing and forwarding\"): a stale network header offset\nreaching a consumer that widens it. Here it originates in the MPLS\npush/pop path.\n\nClear inner_protocol once the packet is no longer MPLS, so a later push\nre-records the current header. net/sched/act_mpls.c is the only other\nskb_mpls_pop() caller and gets the same fix; sch_frag.c saves and\nrestores inner_protocol around fragmentation in the same way OVS does."
        }
      ],
      "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 stale inner_network_header comes from OVS flow actions (push_mpls, pop_mpls, recirc, push_mpls) that the attacker installs over the ovs_flow/ovs_packet generic netlink families. No field of a received packet causes the bad offset, so the vector is local netlink rather than the wire.\nAC:L - The attacker chooses the flow action sequence and the oversized packet that sends do_output into ovs_fragment(). skb_mpls_pop() then deterministically leaves inner_protocol set, and the negative offset always passes the signed MAX_L2_LEN check, so nothing depends on timing or outside state.\nPR:L - The OVS datapath, vport, flow and packet genl operations use GENL_UNS_ADMIN_PERM with netnsok=true. That means CAP_NET_ADMIN inside an unprivileged user and network namespace (unshare -Urn) is enough to create a datapath, install the flows and execute packets.\nUI:N - No victim action is needed. The attacker installs the flows and injects or sends the packet themselves inside their own namespace.\nS:U - The overflow corrupts memory of the same kernel that performs the check. This is ordinary in-kernel memory corruption and crosses no hypervisor or IOMMU boundary.\nC:H - prepare_frag() turns a negative skb_network_offset() into an unsigned hlen of about 4 GiB and memcpy()s attacker packet bytes past the 30-byte per-CPU ovs_frag_data.l2_data. The write covers exec_level, owner, bh_lock and the per-CPU data that follows, and memory corruption of this kind can be leveraged for information disclosure.\nI:H - This is an out-of-bounds write of attacker-controlled skb data into the per-CPU ovs_pcpu_storage and the per-CPU memory after it, including a task_struct pointer (owner) and lock state. The corruption stays in place if the oops happens in process context (OVS_PACKET_CMD_EXECUTE).\nA:H - The runaway memcpy in prepare_frag() always runs until it hits an unmapped per-CPU page and oopses, as the fix\u0027s reproducer shows (write fault in memcpy from prepare_frag/ovs_fragment). The attacker can repeat this at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:10:16.030Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/55ed97db27bffe29c21fdefd5d25601322c36ff8"
        },
        {
          "url": "https://git.kernel.org/stable/c/833ec2788322306407503b4cfc7745cd1f9d785f"
        },
        {
          "url": "https://git.kernel.org/stable/c/38db09804b2616aa1e2fcdf97f0c3ae8b9dbdd34"
        },
        {
          "url": "https://git.kernel.org/stable/c/0b3425fd0ecd515997956f7bb8a8a576b444ed64"
        },
        {
          "url": "https://git.kernel.org/stable/c/011e17b5cae19b9f6a150923275e41c278de64f0"
        },
        {
          "url": "https://git.kernel.org/stable/c/da8c3a7f5d3137fec4ff60a6248f5f6d66b6a63e"
        },
        {
          "url": "https://git.kernel.org/stable/c/b39120523475d6b436be7f6cb27d48064148a327"
        },
        {
          "url": "https://git.kernel.org/stable/c/78a86d75a70e1e227711c72865c59b1422d0a5ae"
        }
      ],
      "title": "net: mpls: clear inner_protocol when the last label is popped",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-97612",
    "datePublished": "2026-09-25T10:22:21.423Z",
    "dateReserved": "2026-09-24T16:01:01.158Z",
    "dateUpdated": "2026-10-19T09:10:16.030Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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