Vulnerability-Lookup

GHSA-Q3C9-52VX-CGP8

Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 15:31

Details

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.

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98108"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-25T11:17:41Z",
    "severity": "HIGH"
  },
  "details": "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.",
  "id": "GHSA-q3c9-52vx-cgp8",
  "modified": "2026-09-25T15:31:45Z",
  "published": "2026-09-25T12:31:36Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98108"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1074bcc57f741223f9fa82ce6afe5c3d783e4d10"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4ef05db5b08b176a551b4a6287372045998806b0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5d5a625cbc854d4c4f68e4b16fcf6e682d9a9ed1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6cb79e6499228cfdbd4b3301371ce74d01cd2f80"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-98108 (GCVE-0-2026-98108)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:35 – Updated: 2026-09-25 14:42

Title

Bluetooth: L2CAP: fix chan mode for LE_CONN_REQ + EXT_FLOWCTL pchan

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.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/1074bcc57f741223f…
https://git.kernel.org/stable/c/5d5a625cbc854d4c4…
https://git.kernel.org/stable/c/6cb79e6499228cfdb…
https://git.kernel.org/stable/c/4ef05db5b08b176a5…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 15f02b91056253e8cdc592888f431da0731337b8 , < 1074bcc57f741223f9fa82ce6afe5c3d783e4d10 (git) Affected: 15f02b91056253e8cdc592888f431da0731337b8 , < 5d5a625cbc854d4c4f68e4b16fcf6e682d9a9ed1 (git) Affected: 15f02b91056253e8cdc592888f431da0731337b8 , < 6cb79e6499228cfdbd4b3301371ce74d01cd2f80 (git) Affected: 15f02b91056253e8cdc592888f431da0731337b8 , < 4ef05db5b08b176a551b4a6287372045998806b0 (git)
Linux	Linux	Affected: 5.7 Unaffected: 0 , < 5.7 (semver) Unaffected: 6.12.111 , ≤ 6.12.* (semver) Unaffected: 6.18.53 , ≤ 6.18.* (semver) Unaffected: 7.2.7 , ≤ 7.2.* (semver) Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)

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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",
          "versions": [
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              "lessThan": "1074bcc57f741223f9fa82ce6afe5c3d783e4d10",
              "status": "affected",
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              "versionType": "git"
            },
            {
              "lessThan": "5d5a625cbc854d4c4f68e4b16fcf6e682d9a9ed1",
              "status": "affected",
              "version": "15f02b91056253e8cdc592888f431da0731337b8",
              "versionType": "git"
            },
            {
              "lessThan": "6cb79e6499228cfdbd4b3301371ce74d01cd2f80",
              "status": "affected",
              "version": "15f02b91056253e8cdc592888f431da0731337b8",
              "versionType": "git"
            },
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              "status": "affected",
              "version": "15f02b91056253e8cdc592888f431da0731337b8",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
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            "net/bluetooth/l2cap_core.c"
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          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.7"
            },
            {
              "lessThan": "5.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "versionType": "original_commit_for_fix"
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        }
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      "cpeApplicability": [
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          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.111",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.53",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.7",
                  "versionStartIncluding": "5.7",
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                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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              "negate": false,
              "operator": "OR"
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        {
          "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": [
        {
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
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          },
          "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": "2026-09-25T14:42:05.463Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/6cb79e6499228cfdbd4b3301371ce74d01cd2f80"
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        {
          "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": "2026-09-25T14:42:05.463Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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GHSA-Q3C9-52VX-CGP8

CVE-2026-98108 (GCVE-0-2026-98108)

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