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.)
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.)
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
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| Vendors | Products |
|---|---|
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Linux
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Linux Kernel
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Advisories
| Source | ID | Title |
|---|---|---|
 Ubuntu USN |
USN-8593-1 | Linux kernel vulnerabilities |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Wed, 22 Jul 2026 00:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-120 | |
| References |
| |
| Metrics |
threat_severity
|
threat_severity
|
Wed, 22 Jul 2026 00:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-122 CWE-787 |
Mon, 20 Jul 2026 14:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
cvssV3_1
|
Sun, 19 Jul 2026 15:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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.) | |
| Title | scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-07-20T13:41:13.237Z
Reserved: 2026-07-19T07:54:57.018Z
Link: CVE-2026-63887
Vulnrichment
No data.
NVD
No data.
Redhat
OpenCVE Enrichment
Updated: 2026-07-21T23:45:13Z