CVE-2026-98108 (GCVE-0-2026-98108)
Vulnerability from cvelistv5
Published
2026-09-25 10:35
Modified
2026-10-19 09:14
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: Bluetooth: L2CAP: fix chan mode for LE_CONN_REQ + EXT_FLOWCTL pchan l2cap_new_connection() sets default value of channel mode to match the parent channel. l2cap_le_connect_req() left this at the default, and created L2CAP_MODE_EXT_FLOWCTL channels if listening pchan has that mode. This causes FLAG_DEFER_SETUP channels to reply to L2CAP_LE_CONN_REQ with L2CAP_ECRED_CONN_RSP, which is incorrect. It can also result to stack OOB write (of l2cap_alloc_cid determined values) in l2cap_ecred_rsp_defer(), as l2cap_le_connect_req() does not limit maximum number of deferred channels or check for duplicate ident. Fix by setting chan->mode correctly in l2cap_le_connect_req(). Also check channel mode in l2cap_ecred_rsp_defer(), and do WARN_ON_ONCE instead of OOB write to make it less brittle.
References
Impacted products
Vendor Product Version
Linux Linux Version: 15f02b91056253e8cdc592888f431da0731337b8
Version: 15f02b91056253e8cdc592888f431da0731337b8
Version: 15f02b91056253e8cdc592888f431da0731337b8
Version: 15f02b91056253e8cdc592888f431da0731337b8
Version: 15f02b91056253e8cdc592888f431da0731337b8
Version: 15f02b91056253e8cdc592888f431da0731337b8
Version: 15f02b91056253e8cdc592888f431da0731337b8
Version: 15f02b91056253e8cdc592888f431da0731337b8
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/bluetooth/l2cap_core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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          "product": "Linux",
          "programFiles": [
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "status": "unaffected",
              "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": "5.7",
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                {
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: fix chan mode for LE_CONN_REQ + EXT_FLOWCTL pchan\n\nl2cap_new_connection() sets default value of channel mode to match the\nparent channel.  l2cap_le_connect_req() left this at the default, and\ncreated L2CAP_MODE_EXT_FLOWCTL channels if listening pchan has that\nmode.  This causes FLAG_DEFER_SETUP channels to reply to\nL2CAP_LE_CONN_REQ with L2CAP_ECRED_CONN_RSP, which is incorrect.\n\nIt can also result to stack OOB write (of l2cap_alloc_cid determined\nvalues) in l2cap_ecred_rsp_defer(), as l2cap_le_connect_req() does not\nlimit maximum number of deferred channels or check for duplicate ident.\n\nFix by setting chan-\u003emode correctly in l2cap_le_connect_req().\n\nAlso check channel mode in l2cap_ecred_rsp_defer(), and do WARN_ON_ONCE\ninstead of OOB write to make it less brittle."
        }
      ],
      "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 - The malformed input is a series of L2CAP_LE_CONN_REQ signalling commands, all using the same ident, sent over a BLE link to l2cap_le_connect_req(). The attacker must be within Bluetooth radio range, so the vector is Adjacent.\nAC:H - The OOB write only happens if the target runs an LE listener in BT_MODE_EXT_FLOWCTL with DEFER_SETUP, whose children inherit EXT_FLOWCTL through l2cap_new_connection(). The attacker cannot create that listener. Once it exists, the attacker controls how many LE_CONN_REQs share one ident, and the service\u0027s own recvmsg() triggers the write.\nPR:N - l2cap_le_connect_req() only checks the listener\u0027s sec_level through smp_sufficient_security(). An LE listener defaults to BT_SECURITY_LOW, so an unpaired peer can open the channels, and Just Works pairing is available otherwise.\nUI:N - No human action is needed. The listening service\u0027s normal accept/recvmsg on a deferred child calls l2cap_sock_recvmsg(), which then calls __l2cap_ecred_conn_rsp_defer().\nS:U - The memory corruption stays within the kernel\u0027s own security authority. No VM or hardware isolation boundary is crossed.\nC:H - l2cap_ecred_rsp_defer() writes CIDs past the 5-entry scid[] into the adjacent \u0027count\u0027 field, which then steers later writes to attacker-influenced offsets on the kernel stack. Corruption of this kind can be leveraged for disclosure.\nI:H - This is an out-of-bounds write on the kernel stack in __l2cap_ecred_conn_rsp_defer(). The written values are l2cap_alloc_cid() CIDs whose count and order the attacker influences, and the write can reach the saved frame state.\nA:H - Stack corruption in __l2cap_ecred_conn_rsp_defer() causes a stack-protector panic or an oops, crashing the kernel, and the peer can repeat it."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:14:00.739Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ad0f44a3f1f688558ed876a0702bc2c82b0df689"
        },
        {
          "url": "https://git.kernel.org/stable/c/564ae0e05e598aa895b9dbd18cb7d6eb64752869"
        },
        {
          "url": "https://git.kernel.org/stable/c/aab17938998b29e75c3324763411aef3e300fc67"
        },
        {
          "url": "https://git.kernel.org/stable/c/0e1fc7cab95ad958e55d70a5dfaaea687c9c639f"
        },
        {
          "url": "https://git.kernel.org/stable/c/1074bcc57f741223f9fa82ce6afe5c3d783e4d10"
        },
        {
          "url": "https://git.kernel.org/stable/c/5d5a625cbc854d4c4f68e4b16fcf6e682d9a9ed1"
        },
        {
          "url": "https://git.kernel.org/stable/c/6cb79e6499228cfdbd4b3301371ce74d01cd2f80"
        },
        {
          "url": "https://git.kernel.org/stable/c/4ef05db5b08b176a551b4a6287372045998806b0"
        }
      ],
      "title": "Bluetooth: L2CAP: fix chan mode for LE_CONN_REQ + EXT_FLOWCTL pchan",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98108",
    "datePublished": "2026-09-25T10:35:56.935Z",
    "dateReserved": "2026-09-25T10:25:14.316Z",
    "dateUpdated": "2026-10-19T09:14:00.739Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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