CVE-2026-63887

Status: UPDATED  |  Advisory ID: CVE-2026-63887

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf

iscsi_encode_text_output() concatenates "key=value\0" records into

login->rsp_buf, an 8192-byte kzalloc(MAX_KEY_VALUE_PAIRS) buffer

allocated in iscsit_alloc_login_setup_buffer(). The three sprintf() call

sites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check

the remaining buffer capacity:

*length += sprintf(output_buf, "%s=%s", er->key, er->value);

*length += 1;

output_buf = textbuf + *length;

The 8192-byte ceiling at iscsi_target_check_login_request() bounds the

*input* Login PDU payload, but a single PDU can carry up to 2048 minimal

four-byte "a=b\0" pairs, each unknown key expanding to a 16-byte

"a=NotUnderstood\0" output record via iscsi_add_notunderstood_response().

2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB

heap overrun in the kmalloc-8k slab.

The fix introduces a static iscsi_encode_text_record() helper that uses

snprintf() with a per-call bounds check against the remaining buffer,

and threads a u32 textbuf_size parameter through

iscsi_encode_text_output(). Both call sites in

iscsi_target_handle_csg_zero() (PHASE_SECURITY) and

iscsi_target_handle_csg_one() (PHASE_OPERATIONAL) pass

MAX_KEY_VALUE_PAIRS. On overflow the encoder logs the condition, calls

iscsi_release_extra_responses() to drop queued records, and returns -1;

both caller sites now emit ISCSI_STATUS_CLS_INITIATOR_ERR /

ISCSI_LOGIN_STATUS_INIT_ERR via iscsit_tx_login_rsp() before returning,

so the initiator sees an explicit failed-login response rather than a

silent connection drop. (Prior to this patch only the PHASE_OPERATIONAL

caller did that; the PHASE_SECURITY caller is converted to the same

shape.) (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References