CVE-2026-98555 (GCVE-0-2026-98555)
Vulnerability from cvelistv5
Published
2026-10-18 15:18
Modified
2026-10-24 14:09
Severity ?
7.5 (High) - CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: llc: fix skb UAF and leaks on llc_mac_hdr_init() failure In llc_conn_ac_resend_i_xxx_x_set_0_or_send_rr(), if llc_mac_hdr_init() fails, kfree_skb(skb) is called instead of kfree_skb(nskb). This leaks the newly allocated nskb, reads from the freed skb via LLC_I_GET_NR(pdu), and double-frees skb when llc_conn_state_process() drops its reference. In llc_sap_action_send_xid_r() and llc_sap_action_send_test_r(), nskb is leaked if llc_mac_hdr_init() returns an error. Free nskb in all three error paths.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/llc/llc_c_ac.c",
            "net/llc/llc_s_ac.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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        },
        {
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          "product": "Linux",
          "programFiles": [
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            "net/llc/llc_s_ac.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "2.6.12"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "5.10.271",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "5.15.222",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.189",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver"
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.112",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.55",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "vulnerable": true
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                  "versionEndExcluding": "5.15.222",
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                  "vulnerable": true
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                  "versionEndExcluding": "6.1.189",
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                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.158",
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                  "vulnerable": true
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                {
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                  "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\nllc: fix skb UAF and leaks on llc_mac_hdr_init() failure\n\nIn llc_conn_ac_resend_i_xxx_x_set_0_or_send_rr(), if llc_mac_hdr_init()\nfails, kfree_skb(skb) is called instead of kfree_skb(nskb). This leaks\nthe newly allocated nskb, reads from the freed skb via LLC_I_GET_NR(pdu),\nand double-frees skb when llc_conn_state_process() drops its reference.\n\nIn llc_sap_action_send_xid_r() and llc_sap_action_send_test_r(), nskb is\nleaked if llc_mac_hdr_init() returns an error.\n\nFree nskb in all three error paths."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:A - An adjacent peer can send an IEEE 802.2 LLC2 I-format response with F=1 and N(S)=vR; llc_rcv() through llc_conn_handler() and llc_conn_state_process() reaches the patched action in AWAIT or AWAIT_REJ. LLC2 frames require the same VLAN or Layer-2 domain.\nAC:H - The peer can establish via SABME and withhold replies until the poll timer creates AWAIT, but the UAF also requires llc_mac_hdr_init() to fail. On the relevant VLAN path this requires skb_cow_head() to return -ENOMEM or an admin-driven device/headroom change, which the Layer-2 peer cannot reliably control.\nPR:N - llc_rcv() and llc_conn_handler() perform no peer authentication; a peer can send SABME and the triggering I response without local credentials. CAP_NET_RAW in llc_ui_create() constrains the host process creating the listener, not the remote peer.\nUI:N - Once the LLC listener exists, llc_conn_handler() creates and drives the incoming socket before userspace accept(), while the peer supplies the SABME, waits for the timer state, and sends the triggering I response. No further victim action is required.\nS:U - llc_conn_ac_resend_i_xxx_x_set_0_or_send_rr() corrupts an skb owned by the host LLC stack, and all resulting effects remain within the same host-kernel security authority.\nC:H - The erroneous kfree_skb(skb) leaves pdu dangling, after which LLC_I_GET_NR(pdu) reads the freed object and llc_conn_state_process() continues using the same skb. Reuse of that slab object can expose attacker-influenced kernel memory.\nI:H - After the action frees the incoming skb, llc_conn_state_process() later calls kfree_skb(skb) again. Reallocation between these operations permits freed-object manipulation and allocator corruption capable of write or control-flow impact.\nA:H - The use-after-free culminates in a second kfree_skb() of the received frame in llc_conn_state_process(), which can cause a kernel oops, allocator failure, or panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:09:24.593Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/fec0fe6838a7f45175667701fb51abb23a6ffb1e"
        },
        {
          "url": "https://git.kernel.org/stable/c/b859ba18b5a1067f71db5618c6a4a70d55fa308b"
        },
        {
          "url": "https://git.kernel.org/stable/c/8b855b645841b5a04e20339a22bb6d593c9b790d"
        },
        {
          "url": "https://git.kernel.org/stable/c/d360b31f1a3666579422872aa7d1a751e20b76f9"
        },
        {
          "url": "https://git.kernel.org/stable/c/060f827aa3dc47939ee306da715cd6700d129616"
        },
        {
          "url": "https://git.kernel.org/stable/c/41dcae82bece9f106b4dff0ee777bba8d157c8a8"
        },
        {
          "url": "https://git.kernel.org/stable/c/cb3528ad8bb46fa6252f5d14ced7febddc18515d"
        },
        {
          "url": "https://git.kernel.org/stable/c/72f9dd522f8d6c5a00be9695c7bb74631eb5069e"
        }
      ],
      "title": "llc: fix skb UAF and leaks on llc_mac_hdr_init() failure",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98555",
    "datePublished": "2026-10-18T15:18:22.631Z",
    "dateReserved": "2026-09-25T10:25:14.357Z",
    "dateUpdated": "2026-10-24T14:09:24.593Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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