Linux Kernel L2CAP: Stack OOB Read in l2cap_ecred_conn_req
CVE-2026-31513 Published on April 22, 2026
Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req
Syzbot reported a KASAN stack-out-of-bounds read in l2cap_build_cmd()
that is triggered by a malformed Enhanced Credit Based Connection Request.
The vulnerability stems from l2cap_ecred_conn_req(). The function allocates
a local stack buffer (`pdu`) designed to hold a maximum of 5 Source Channel
IDs (SCIDs), totaling 18 bytes. When an attacker sends a request with more
than 5 SCIDs, the function calculates `rsp_len` based on this unvalidated
`cmd_len` before checking if the number of SCIDs exceeds
L2CAP_ECRED_MAX_CID.
If the SCID count is too high, the function correctly jumps to the
`response` label to reject the packet, but `rsp_len` retains the
attacker's oversized value. Consequently, l2cap_send_cmd() is instructed
to read past the end of the 18-byte `pdu` buffer, triggering a
KASAN panic.
Fix this by moving the assignment of `rsp_len` to after the `num_scid`
boundary check. If the packet is rejected, `rsp_len` will safely
remain 0, and the error response will only read the 8-byte base header
from the stack.
Products Associated with CVE-2026-31513
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Affected Versions
Linux:- Version 935f324e4b2461df2cf7f02b4195082b4304c708 and below c8e1a27edb8b4e5afb56b384acd7b6c2dec1b7cc is affected.
- Version e981a9392800ce2c5bca196a6ab2c55e9370efaa and below 5b35f8211a913cfe7ab9d54fa36a272d2059a588 is affected.
- Version f3fdf2e7276a3edc5df55454275da20eac186970 and below a3d9c50d69785ae02e153f000da1b5fd6dbfdf1b is affected.
- Version c28d2bff70444a85b3b86aaf241ece9408c7858c and below 9d87cb22195b2c67405f5485d525190747ad5493 is affected.
- Version 6.12.75 and below 6.12.80 is affected.
- Version 6.18.16 and below 6.18.21 is affected.
- Version 6.19.6 and below 6.19.11 is affected.