CVE-2026-64127 (GCVE-0-2026-64127)

Vulnerability from cvelistv5 – Published: 2026-07-19 15:40 – Updated: 2026-07-19 15:40
VLAI
Title
Bluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack pointer
Summary
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack pointer Commit 1c08108f3014 ("Bluetooth: L2CAP: Avoid -Wflex-array-member-not-at-end warnings") converted the on-stack request PDU in l2cap_ecred_reconfigure() from an explicit packed struct to DEFINE_RAW_FLEX(), but did not adjust the size and source-pointer arguments to l2cap_send_cmd(): - struct { - struct l2cap_ecred_reconf_req req; - __le16 scid; - } pdu; + DEFINE_RAW_FLEX(struct l2cap_ecred_reconf_req, pdu, scid, 1); ... l2cap_send_cmd(conn, chan->ident, L2CAP_ECRED_RECONF_REQ, sizeof(pdu), &pdu); After the conversion, DEFINE_RAW_FLEX() expands to declare an anonymous union pdu_u plus a local pointer "pdu" pointing at it. Therefore: - sizeof(pdu) is now sizeof(struct l2cap_ecred_reconf_req *) = 8 on 64-bit (4 on 32-bit), not the 6 bytes of (mtu, mps, scid[1]). - &pdu is the address of the local pointer's stack storage, not the address of the request payload. l2cap_send_cmd() forwards (data, count) to l2cap_build_cmd(), which calls skb_put_data(skb, data, count). The L2CAP_ECRED_RECONFIGURE_REQ packet body therefore contains 8 bytes copied from the kernel stack starting at &pdu -- the 8 bytes overlap the pdu pointer's value, leaking a kernel stack address to the paired Bluetooth peer. The intended (mtu, mps, scid) fields are not transmitted at all, so the peer rejects the request as malformed and the L2CAP_ECRED_RECONFIGURE feature itself has been broken for the local-side initiator since the introducing commit landed. The sibling site l2cap_ecred_conn_req() in the same commit was converted correctly (sizeof(*pdu) + len, pdu); only this site was missed. Restore the original semantics: pass the full flex-struct size via struct_size(pdu, scid, 1) and the pdu pointer (the struct address) as the source. Validated on a stock 7.0-based host kernel via the real call path: setsockopt(SOL_BLUETOOTH, BT_RCVMTU, ...) on a BT_CONNECTED L2CAP_MODE_EXT_FLOWCTL socket emits an L2CAP_ECRED_RECONFIGURE_REQ whose body is 8 bytes (the on-stack pdu local's value) rather than the expected 6. Three captures from fresh socket / fresh hciemu peer on the same host -- low bytes vary per call, high 0xffff confirms a kernel virtual address (KASLR-randomised stack slot, not a fixed string): RECONF_REQ body (ident=0x02 len=8): 42 fb 54 af 0e ca ff ff RECONF_REQ body (ident=0x02 len=8): 52 3d 2e af 0e ca ff ff RECONF_REQ body (ident=0x02 len=8): b2 fc 5b af 0e ca ff ff After this patch the body is 6 bytes carrying the expected little-endian (mtu, mps, scid).
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1c08108f3014881ad5f4c35a2abaf9c65475035d , < ed5fcd2a26f0c16fc289c8cd6b03328a0582a687 (git)
Affected: 1c08108f3014881ad5f4c35a2abaf9c65475035d , < 051922ab709c0a6917eae765c22481dfc68379e5 (git)
Affected: 1c08108f3014881ad5f4c35a2abaf9c65475035d , < 356c9d1a1cbacd2a1640fff3c050e1c3472e924f (git)
Affected: 1c08108f3014881ad5f4c35a2abaf9c65475035d , < 3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d (git)
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Linux Linux Affected: 6.10
Unaffected: 0 , < 6.10 (semver)
Unaffected: 6.12.92 , ≤ 6.12.* (semver)
Unaffected: 6.18.34 , ≤ 6.18.* (semver)
Unaffected: 7.0.11 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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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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              "status": "affected",
              "version": "1c08108f3014881ad5f4c35a2abaf9c65475035d",
              "versionType": "git"
            },
            {
              "lessThan": "051922ab709c0a6917eae765c22481dfc68379e5",
              "status": "affected",
              "version": "1c08108f3014881ad5f4c35a2abaf9c65475035d",
              "versionType": "git"
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              "status": "affected",
              "version": "1c08108f3014881ad5f4c35a2abaf9c65475035d",
              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "1c08108f3014881ad5f4c35a2abaf9c65475035d",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/bluetooth/l2cap_core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.10"
            },
            {
              "lessThan": "6.10",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.92",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.34",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.92",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.34",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.11",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack pointer\n\nCommit 1c08108f3014 (\"Bluetooth: L2CAP: Avoid -Wflex-array-member-not-at-end\nwarnings\") converted the on-stack request PDU in l2cap_ecred_reconfigure()\nfrom an explicit packed struct to DEFINE_RAW_FLEX(), but did not adjust the\nsize and source-pointer arguments to l2cap_send_cmd():\n\n  -    struct {\n  -            struct l2cap_ecred_reconf_req req;\n  -            __le16 scid;\n  -    } pdu;\n  +    DEFINE_RAW_FLEX(struct l2cap_ecred_reconf_req, pdu, scid, 1);\n       ...\n       l2cap_send_cmd(conn, chan-\u003eident, L2CAP_ECRED_RECONF_REQ,\n                      sizeof(pdu), \u0026pdu);\n\nAfter the conversion, DEFINE_RAW_FLEX() expands to declare an anonymous\nunion pdu_u plus a local pointer \"pdu\" pointing at it. Therefore:\n\n  - sizeof(pdu) is now sizeof(struct l2cap_ecred_reconf_req *) = 8 on\n    64-bit (4 on 32-bit), not the 6 bytes of (mtu, mps, scid[1]).\n  - \u0026pdu is the address of the local pointer\u0027s stack storage, not the\n    address of the request payload.\n\nl2cap_send_cmd() forwards (data, count) to l2cap_build_cmd(), which calls\nskb_put_data(skb, data, count). The L2CAP_ECRED_RECONFIGURE_REQ packet\nbody therefore contains 8 bytes copied from the kernel stack starting at\n\u0026pdu -- the 8 bytes overlap the pdu pointer\u0027s value, leaking a kernel\nstack address to the paired Bluetooth peer. The intended (mtu, mps, scid)\nfields are not transmitted at all, so the peer rejects the request as\nmalformed and the L2CAP_ECRED_RECONFIGURE feature itself has been broken\nfor the local-side initiator since the introducing commit landed.\n\nThe sibling site l2cap_ecred_conn_req() in the same commit was converted\ncorrectly (sizeof(*pdu) + len, pdu); only this site was missed.\n\nRestore the original semantics: pass the full flex-struct size via\nstruct_size(pdu, scid, 1) and the pdu pointer (the struct address) as\nthe source.\n\nValidated on a stock 7.0-based host kernel via the real call path:\nsetsockopt(SOL_BLUETOOTH, BT_RCVMTU, ...) on a BT_CONNECTED\nL2CAP_MODE_EXT_FLOWCTL socket emits an L2CAP_ECRED_RECONFIGURE_REQ\nwhose body is 8 bytes (the on-stack pdu local\u0027s value) rather than\nthe expected 6. Three captures from fresh socket / fresh hciemu peer\non the same host -- low bytes vary per call, high 0xffff confirms a\nkernel virtual address (KASLR-randomised stack slot, not a fixed\nstring):\n\n  RECONF_REQ body (ident=0x02 len=8): 42 fb 54 af 0e ca ff ff\n  RECONF_REQ body (ident=0x02 len=8): 52 3d 2e af 0e ca ff ff\n  RECONF_REQ body (ident=0x02 len=8): b2 fc 5b af 0e ca ff ff\n\nAfter this patch the body is 6 bytes carrying the expected\nlittle-endian (mtu, mps, scid)."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-19T15:40:23.960Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ed5fcd2a26f0c16fc289c8cd6b03328a0582a687"
        },
        {
          "url": "https://git.kernel.org/stable/c/051922ab709c0a6917eae765c22481dfc68379e5"
        },
        {
          "url": "https://git.kernel.org/stable/c/356c9d1a1cbacd2a1640fff3c050e1c3472e924f"
        },
        {
          "url": "https://git.kernel.org/stable/c/3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d"
        }
      ],
      "title": "Bluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack pointer",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64127",
    "datePublished": "2026-07-19T15:40:23.960Z",
    "dateReserved": "2026-07-19T07:54:57.036Z",
    "dateUpdated": "2026-07-19T15:40:23.960Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-64127",
      "date": "2026-07-21",
      "epss": "0.00175",
      "percentile": "0.07263"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-64127\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-07-19T16:17:54.387\",\"lastModified\":\"2026-07-19T16:17:54.387\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nBluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack pointer\\n\\nCommit 1c08108f3014 (\\\"Bluetooth: L2CAP: Avoid -Wflex-array-member-not-at-end\\nwarnings\\\") converted the on-stack request PDU in l2cap_ecred_reconfigure()\\nfrom an explicit packed struct to DEFINE_RAW_FLEX(), but did not adjust the\\nsize and source-pointer arguments to l2cap_send_cmd():\\n\\n  -    struct {\\n  -            struct l2cap_ecred_reconf_req req;\\n  -            __le16 scid;\\n  -    } pdu;\\n  +    DEFINE_RAW_FLEX(struct l2cap_ecred_reconf_req, pdu, scid, 1);\\n       ...\\n       l2cap_send_cmd(conn, chan-\u003eident, L2CAP_ECRED_RECONF_REQ,\\n                      sizeof(pdu), \u0026pdu);\\n\\nAfter the conversion, DEFINE_RAW_FLEX() expands to declare an anonymous\\nunion pdu_u plus a local pointer \\\"pdu\\\" pointing at it. Therefore:\\n\\n  - sizeof(pdu) is now sizeof(struct l2cap_ecred_reconf_req *) = 8 on\\n    64-bit (4 on 32-bit), not the 6 bytes of (mtu, mps, scid[1]).\\n  - \u0026pdu is the address of the local pointer\u0027s stack storage, not the\\n    address of the request payload.\\n\\nl2cap_send_cmd() forwards (data, count) to l2cap_build_cmd(), which calls\\nskb_put_data(skb, data, count). The L2CAP_ECRED_RECONFIGURE_REQ packet\\nbody therefore contains 8 bytes copied from the kernel stack starting at\\n\u0026pdu -- the 8 bytes overlap the pdu pointer\u0027s value, leaking a kernel\\nstack address to the paired Bluetooth peer. The intended (mtu, mps, scid)\\nfields are not transmitted at all, so the peer rejects the request as\\nmalformed and the L2CAP_ECRED_RECONFIGURE feature itself has been broken\\nfor the local-side initiator since the introducing commit landed.\\n\\nThe sibling site l2cap_ecred_conn_req() in the same commit was converted\\ncorrectly (sizeof(*pdu) + len, pdu); only this site was missed.\\n\\nRestore the original semantics: pass the full flex-struct size via\\nstruct_size(pdu, scid, 1) and the pdu pointer (the struct address) as\\nthe source.\\n\\nValidated on a stock 7.0-based host kernel via the real call path:\\nsetsockopt(SOL_BLUETOOTH, BT_RCVMTU, ...) on a BT_CONNECTED\\nL2CAP_MODE_EXT_FLOWCTL socket emits an L2CAP_ECRED_RECONFIGURE_REQ\\nwhose body is 8 bytes (the on-stack pdu local\u0027s value) rather than\\nthe expected 6. Three captures from fresh socket / fresh hciemu peer\\non the same host -- low bytes vary per call, high 0xffff confirms a\\nkernel virtual address (KASLR-randomised stack slot, not a fixed\\nstring):\\n\\n  RECONF_REQ body (ident=0x02 len=8): 42 fb 54 af 0e ca ff ff\\n  RECONF_REQ body (ident=0x02 len=8): 52 3d 2e af 0e ca ff ff\\n  RECONF_REQ body (ident=0x02 len=8): b2 fc 5b af 0e ca ff ff\\n\\nAfter this patch the body is 6 bytes carrying the expected\\nlittle-endian (mtu, mps, scid).\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/bluetooth/l2cap_core.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"1c08108f3014881ad5f4c35a2abaf9c65475035d\",\"lessThan\":\"ed5fcd2a26f0c16fc289c8cd6b03328a0582a687\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1c08108f3014881ad5f4c35a2abaf9c65475035d\",\"lessThan\":\"051922ab709c0a6917eae765c22481dfc68379e5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1c08108f3014881ad5f4c35a2abaf9c65475035d\",\"lessThan\":\"356c9d1a1cbacd2a1640fff3c050e1c3472e924f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"1c08108f3014881ad5f4c35a2abaf9c65475035d\",\"lessThan\":\"3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/bluetooth/l2cap_core.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.10\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.10\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.92\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.34\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.11\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/051922ab709c0a6917eae765c22481dfc68379e5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/356c9d1a1cbacd2a1640fff3c050e1c3472e924f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ed5fcd2a26f0c16fc289c8cd6b03328a0582a687\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-20T08:22:48+00:00",
      "cve": "CVE-2026-64127",
      "id": "CVE-2026-64127",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "91",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Bluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack pointer",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64127.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.


Detection rules are retrieved from Rulezet.