CVE-2026-64127In 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-…

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).

CVSS

5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness (CWE)

Not given

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

Not loaded for this CVE

Assigned by

Not given

NVD analysis

Analyzed

Record last updated

Aug 13, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

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