CVE-2026-53176

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.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

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.