{"api_version":"1","generated_at":"2026-07-20T14:43:34+00:00","cve":"CVE-2026-64127","urls":{"html":"https://cve.report/CVE-2026-64127","api":"https://cve.report/api/cve/CVE-2026-64127.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-64127","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-64127"},"summary":{"title":"Bluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack pointer","description":"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->ident, L2CAP_ECRED_RECONF_REQ,\n                      sizeof(pdu), &pdu);\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  - &pdu is the address of the local pointer's 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&pdu -- the 8 bytes overlap the pdu pointer's 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's 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).","state":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 16:17:54","updated_at":"2026-07-19 16:17:54"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/ed5fcd2a26f0c16fc289c8cd6b03328a0582a687","name":"https://git.kernel.org/stable/c/ed5fcd2a26f0c16fc289c8cd6b03328a0582a687","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/356c9d1a1cbacd2a1640fff3c050e1c3472e924f","name":"https://git.kernel.org/stable/c/356c9d1a1cbacd2a1640fff3c050e1c3472e924f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d","name":"https://git.kernel.org/stable/c/3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/051922ab709c0a6917eae765c22481dfc68379e5","name":"https://git.kernel.org/stable/c/051922ab709c0a6917eae765c22481dfc68379e5","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-64127","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64127","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 1c08108f3014881ad5f4c35a2abaf9c65475035d ed5fcd2a26f0c16fc289c8cd6b03328a0582a687 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 1c08108f3014881ad5f4c35a2abaf9c65475035d 051922ab709c0a6917eae765c22481dfc68379e5 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 1c08108f3014881ad5f4c35a2abaf9c65475035d 356c9d1a1cbacd2a1640fff3c050e1c3472e924f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 1c08108f3014881ad5f4c35a2abaf9c65475035d 3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.10","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.10 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.92 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.34 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.11 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"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":[{"lessThan":"ed5fcd2a26f0c16fc289c8cd6b03328a0582a687","status":"affected","version":"1c08108f3014881ad5f4c35a2abaf9c65475035d","versionType":"git"},{"lessThan":"051922ab709c0a6917eae765c22481dfc68379e5","status":"affected","version":"1c08108f3014881ad5f4c35a2abaf9c65475035d","versionType":"git"},{"lessThan":"356c9d1a1cbacd2a1640fff3c050e1c3472e924f","status":"affected","version":"1c08108f3014881ad5f4c35a2abaf9c65475035d","versionType":"git"},{"lessThan":"3374ef8cf99368a40f7efd51a2a375a4c5dc6f0d","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->ident, L2CAP_ECRED_RECONF_REQ,\n                      sizeof(pdu), &pdu);\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  - &pdu is the address of the local pointer's 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&pdu -- the 8 bytes overlap the pdu pointer's 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's 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"},"nvd":{"publishedDate":"2026-07-19 16:17:54","lastModifiedDate":"2026-07-19 16:17:54","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"64127","Ordinal":"1","Title":"Bluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack ","CVE":"CVE-2026-64127","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"64127","Ordinal":"1","NoteData":"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->ident, L2CAP_ECRED_RECONF_REQ,\n                      sizeof(pdu), &pdu);\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  - &pdu is the address of the local pointer's 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&pdu -- the 8 bytes overlap the pdu pointer's 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's 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).","Type":"Description","Title":"Bluetooth: L2CAP: ecred_reconfigure: send packed pdu, not stack "}]}}}