Buffer Overflow Affecting kernel-rt-64k-devel-matched package, versions *


Severity

Recommended
0.0
high
0
10

Based on CentOS security rating.

Threat Intelligence

EPSS
0.75% (51st percentile)

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  • Snyk IDSNYK-CENTOS9-KERNELRT64KDEVELMATCHED-18250710
  • published23 Jul 2026
  • disclosed19 Jul 2026

Introduced: 19 Jul 2026

NewCVE-2026-63887  (opens in a new tab)
CWE-120  (opens in a new tab)

How to fix?

There is no fixed version for Centos:9 kernel-rt-64k-devel-matched.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-64k-devel-matched package and not the kernel-rt-64k-devel-matched package as distributed by Centos. See How to fix? for Centos:9 relevant fixed versions and status.

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.)

CVSS Base Scores

version 3.1