Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-06-25T00:00:00 kernel: IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CWE-839

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.

A flaw was found in the Linux kernel's Internet Small Computer System Interface (iSCSI) Extensions for Remote Direct Memory Access (RDMA) (iSER) module. A remote attacker can send a specially crafted login request with a payload shorter than expected, leading to an integer underflow. This underflow causes a negative length to be used in a memory copy operation, resulting in an out-of-bounds write that crashes the system. This vulnerability allows an unauthenticated remote attacker to cause a Denial of Service (DoS).

An out-of-bounds memcpy in the iSER target login path can occur because isert_login_recv_done subtracts ISER_HEADERS_LEN from wc byte_len without first checking that the received login PDU is at least that large. A remote iSER initiator can send a login Send work request shorter than ISER_HEADERS_LEN before iSCSI authentication, making login_req_len negative and later sign extending it into a very large memcpy length into an 8192-byte login buffer. The issue is network reachable on the RDMA or storage fabric, but AV:A is used because iSER deployments are normally limited to adjacent storage or data center networks rather than the public Internet. Impact is denial of service via target kernel crash. To mitigate this issue, prevent module ib_isert from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically. Red Hat Enterprise Linux 10 Affected kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Affected kernel Red Hat Enterprise Linux 7 Affected kernel-rt Red Hat Enterprise Linux 8 Affected kernel Red Hat Enterprise Linux 8 Affected kernel-rt Red Hat Enterprise Linux 9 Affected kernel Red Hat Enterprise Linux 9 Affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-53176 https://nvd.nist.gov/vuln/detail/CVE-2026-53176 https://lore.kernel.org/linux-cve-announce/2026062553-CVE-2026-53176-c8a7@gregkh/T