CVE-2026-53176
CriticalCVSS 9.8Exploitation Probability (EPSS)
Elevated risk50th percentile - higher than 50% of all known CVEs
Summary
In the Linux kernel's IB/isert driver, a missing lower bound check on iSER login PDU length allows a remote initiator to send a packet shorter than ISER_HEADERS_LEN (76 bytes). This causes an underflow in payload length calculation, leading to a buffer overflow during memcpy and a crash of the target node. No authentication is required to exploit this vulnerability.
Risk Assessment
The risk is a remote denial-of-service (crash) of the iSCSI target node without any credentials. This can disrupt storage services and potentially cause data unavailability.
Recommendation
Apply the security patch provided by your Linux kernel distributor immediately. If patching is not possible, restrict iSER service access to trusted networks and hosts only.
Original NVD description (English source)
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.