CVE-2026-63887

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf<br /> <br /> iscsi_encode_text_output() concatenates "key=value\0" records into<br /> login-&gt;rsp_buf, an 8192-byte kzalloc(MAX_KEY_VALUE_PAIRS) buffer<br /> allocated in iscsit_alloc_login_setup_buffer(). The three sprintf() call<br /> sites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check<br /> the remaining buffer capacity:<br /> <br /> *length += sprintf(output_buf, "%s=%s", er-&gt;key, er-&gt;value);<br /> *length += 1;<br /> output_buf = textbuf + *length;<br /> <br /> The 8192-byte ceiling at iscsi_target_check_login_request() bounds the<br /> *input* Login PDU payload, but a single PDU can carry up to 2048 minimal<br /> four-byte "a=b\0" pairs, each unknown key expanding to a 16-byte<br /> "a=NotUnderstood\0" output record via iscsi_add_notunderstood_response().<br /> 2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB<br /> heap overrun in the kmalloc-8k slab.<br /> <br /> The fix introduces a static iscsi_encode_text_record() helper that uses<br /> snprintf() with a per-call bounds check against the remaining buffer,<br /> and threads a u32 textbuf_size parameter through<br /> iscsi_encode_text_output(). Both call sites in<br /> iscsi_target_handle_csg_zero() (PHASE_SECURITY) and<br /> iscsi_target_handle_csg_one() (PHASE_OPERATIONAL) pass<br /> MAX_KEY_VALUE_PAIRS. On overflow the encoder logs the condition, calls<br /> iscsi_release_extra_responses() to drop queued records, and returns -1;<br /> both caller sites now emit ISCSI_STATUS_CLS_INITIATOR_ERR /<br /> ISCSI_LOGIN_STATUS_INIT_ERR via iscsit_tx_login_rsp() before returning,<br /> so the initiator sees an explicit failed-login response rather than a<br /> silent connection drop. (Prior to this patch only the PHASE_OPERATIONAL<br /> caller did that; the PHASE_SECURITY caller is converted to the same<br /> shape.)