CVE-2026-53176

In the Linux kernel, the following vulnerability has been resolved:

IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN

In drivers/infiniband/ulp/isert/ib_isert.c, isert_login_recv_done()

computes the login request payload length as wc->byte_len minus

ISER_HEADERS_LEN with no lower bound, and login_req_len is a signed int.

A remote iSER initiator can post a login Send work request carrying

fewer than ISER_HEADERS_LEN (76) bytes, so the subtraction underflows

and login_req_len becomes negative.

isert_rx_login_req() then reads that negative length back into a signed

int, takes size = min(rx_buflen, MAX_KEY_VALUE_PAIRS), and because the

min() is signed it keeps the negative value; the value is then passed as

the memcpy() length and sign-extended to a multi-gigabyte size_t. The

copy into the 8192-byte login->req_buf runs far out of bounds and

faults, crashing the target node. The login phase precedes iSCSI

authentication, so no credentials are required to reach this path.

Reject any login PDU shorter than ISER_HEADERS_LEN before the

subtraction, mirroring the existing early return on a failed work

completion, so login_req_len can never go negative. The upper bound was

already safe: a posted login buffer cannot deliver more than

ISER_RX_PAYLOAD_SIZE, so the difference stays at or below

MAX_KEY_VALUE_PAIRS and the existing min() clamps it; only the missing

lower bound needs to be added.