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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63887
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:05 UTC
Updated2026-07-20 15:16:54 UTC
DescriptionIn 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.)

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.002200000 probability, percentile 0.125280000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 cb84e974fb172bc71386289f37b78ea679410b39 git Not specified
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 b19382dfc6e7dee6d3859ba44b6ca29e97a51627 git Not specified
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 efe633e600a0ac68357206fede21b1ac8178f3b8 git Not specified
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 4e9f0c4a645c995bc75c06c7b3644254ffb4c76b git Not specified
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 30bf335e8fe170322080ee001f05ca29c50680b3 git Not specified
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 594a40360012ce5f94c715d5e3b20fa3af7d525a git Not specified
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 26e4a304b7e6f1338c675d527608d32549c091db git Not specified
CNA Linux Linux affected e48354ce078c079996f89d715dfa44814b4eba01 bf33e01f88388c43e285492a63e539df6ffed64c git Not specified
CNA Linux Linux affected 3.1 Not specified
CNA Linux Linux unaffected 3.1 semver Not specified
CNA Linux Linux unaffected 5.10.259 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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