SEPTEMBER 17, 2026
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Case File

CVE-2026-74556

CRITICAL · CVSS 9.8 EPSS 0.40%

Source: NVD + CISA KEV + EPSS · Published 2026-08-15 · Last synced 2026-09-14

CyberRota Analysis

AI-Generated

The vulnerability affects the Linux kernel's handling of SCSI Command Responses in the iSCSI protocol, specifically in the iscsi_tcp_hdr_dissect() function, which fails to properly limit the size of data segments copied into a fixed-size buffer. This oversight can lead to buffer overflow conditions when a target returns a SCSI Response with a DataSegmentLength exceeding the buffer size, potentially allowing for arbitrary code execution or system crashes. Organizations using Linux systems with iSCSI implementations should prioritize patching this vulnerability to mitigate the risk of exploitation.

CVE
CVE-2026-74556
Severity
CRITICAL
CVSS
9.8
EPSS
0.40%
Linux

Original NVD Description

In the Linux kernel, the following vulnerability has been resolved: scsi: libiscsi_tcp: Bound SCSI Response data segment to the connection buffer iscsi_tcp_hdr_dissect() receives the data segment of several PDU types into the fixed-size conn->data buffer, which is allocated for ISCSI_DEF_MAX_RECV_SEG_LEN (8192) bytes. For the LOGIN_RSP, TEXT_RSP, REJECT and ASYNC_EVENT opcodes the dissect path already rejects a PDU whose DataSegmentLength exceeds that buffer. The SCSI Command Response (ISCSI_OP_SCSI_CMD_RSP) path also copies its data segment (sense/response data) into conn->data via iscsi_tcp_data_recv_prep(), but it does so without the same check. The only upstream bound on in.datalen is conn->max_recv_dlength, the initiator's advertised MaxRecvDataSegmentLength, which is commonly negotiated well above 8192 (open-iscsi defaults to 262144). A target that returns a SCSI Response with a DataSegmentLength between 8193 and max_recv_dlength therefore overflows the 8192-byte conn->data buffer. Once the same bound applies, ISCSI_OP_SCSI_CMD_RSP is handled exactly like those responses: bound the data segment, receive it into conn->data when present, and otherwise complete the PDU with no data. Fold the opcode into that case group rather than duplicating the check.