{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63887", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.018Z", "datePublished": "2026-07-19T14:55:00.114Z", "dateUpdated": "2026-08-05T12:36:56.451Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:36:56.451Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf\n\niscsi_encode_text_output() concatenates \"key=value\\0\" records into\nlogin->rsp_buf, an 8192-byte kzalloc(MAX_KEY_VALUE_PAIRS) buffer\nallocated in iscsit_alloc_login_setup_buffer(). The three sprintf() call\nsites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check\nthe remaining buffer capacity:\n\n\t*length += sprintf(output_buf, \"%s=%s\", er->key, er->value);\n\t*length += 1;\n\toutput_buf = textbuf + *length;\n\nThe 8192-byte ceiling at iscsi_target_check_login_request() bounds the\n*input* Login PDU payload, but a single PDU can carry up to 2048 minimal\nfour-byte \"a=b\\0\" pairs, each unknown key expanding to a 16-byte\n\"a=NotUnderstood\\0\" output record via iscsi_add_notunderstood_response().\n2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB\nheap overrun in the kmalloc-8k slab.\n\nThe fix introduces a static iscsi_encode_text_record() helper that uses\nsnprintf() with a per-call bounds check against the remaining buffer,\nand threads a u32 textbuf_size parameter through\niscsi_encode_text_output(). Both call sites in\niscsi_target_handle_csg_zero() (PHASE_SECURITY) and\niscsi_target_handle_csg_one() (PHASE_OPERATIONAL) pass\nMAX_KEY_VALUE_PAIRS. On overflow the encoder logs the condition, calls\niscsi_release_extra_responses() to drop queued records, and returns -1;\nboth caller sites now emit ISCSI_STATUS_CLS_INITIATOR_ERR /\nISCSI_LOGIN_STATUS_INIT_ERR via iscsit_tx_login_rsp() before returning,\nso the initiator sees an explicit failed-login response rather than a\nsilent connection drop. (Prior to this patch only the PHASE_OPERATIONAL\ncaller did that; the PHASE_SECURITY caller is converted to the same\nshape.)" } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The Linux iSCSI target (LIO) is an in-kernel SCSI target that accepts remote TCP connections on the iSCSI portal (typically port 3260); crafted Login PDUs reach the vulnerable encoder via the normal network receive and login-negotiation path.\nAC:L - Once an iSCSI target portal is reachable, an attacker can reliably trigger the overflow by sending a single Login PDU packed with unknown key=value pairs; no races or victim-dependent timing are required.\nPR:N - The heap overflow occurs during login negotiation before iSCSI authentication completes; a discovery-session login requires only InitiatorName and SessionType with no credentials, initiator ACL, or local privileges.\nUI:N - Exploitation requires only network packets sent by the attacker; no action from a legitimate user or administrator is needed beyond the target already exposing its iSCSI portal.\nS:U - The corruption is confined to kernel heap memory in the iSCSI target/login context and does not cross a VM, container, or IOMMU security boundary by itself.\nC:H - A ~24 KiB out-of-bounds write into the kmalloc-8k slab can corrupt adjacent kernel objects and be leveraged for arbitrary memory disclosure, not merely a bounded leak.\nI:H - The unbounded sprintf heap overrun is a large out-of-bounds write that can corrupt adjacent heap metadata or objects to achieve arbitrary kernel memory modification and potential code execution.\nA:H - Corrupting kmalloc-8k heap objects during login response encoding can cause kernel oops, BUG, or panic, and the attack can be repeated against an exposed iSCSI target." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/target/iscsi/iscsi_target_nego.c", "drivers/target/iscsi/iscsi_target_parameters.c", "drivers/target/iscsi/iscsi_target_parameters.h" ], "versions": [ { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "cb84e974fb172bc71386289f37b78ea679410b39", "status": "affected", "versionType": "git" }, { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "b19382dfc6e7dee6d3859ba44b6ca29e97a51627", "status": "affected", "versionType": "git" }, { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "efe633e600a0ac68357206fede21b1ac8178f3b8", "status": "affected", "versionType": "git" }, { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "4e9f0c4a645c995bc75c06c7b3644254ffb4c76b", "status": "affected", "versionType": "git" }, { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "30bf335e8fe170322080ee001f05ca29c50680b3", "status": "affected", "versionType": "git" }, { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "594a40360012ce5f94c715d5e3b20fa3af7d525a", "status": "affected", "versionType": "git" }, { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "26e4a304b7e6f1338c675d527608d32549c091db", "status": "affected", "versionType": "git" }, { "version": "e48354ce078c079996f89d715dfa44814b4eba01", "lessThan": "bf33e01f88388c43e285492a63e539df6ffed64c", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/target/iscsi/iscsi_target_nego.c", "drivers/target/iscsi/iscsi_target_parameters.c", "drivers/target/iscsi/iscsi_target_parameters.h" ], "versions": [ { "version": "3.1", "status": "affected" }, { "version": "0", "lessThan": "3.1", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.259", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.210", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.176", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.143", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.35", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "5.10.259" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "5.15.210" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "6.1.176" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "6.6.143" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "6.18.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.1", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39" }, { "url": "https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627" }, { "url": "https://git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8" }, { "url": "https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b" }, { "url": "https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3" }, { "url": "https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a" }, { "url": "https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db" }, { "url": "https://git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c" } ], "title": "scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf", 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