{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-63887", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-63887" ], "published": "2026-07-19T14:56:29Z", "summary": "scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf", "details": "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.)", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.176", "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-63887" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 9.8, "cvss_v3_severity": "Critical", "scenario": "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." } } }