{"cve":"CVE-2026-63887","nvd":{"published":"2026-07-19T16:17:05.853","modified":"2026-10-22T14:33:17.540","status":"Analyzed","description":"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.)","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":["CWE-120","CWE-122"],"references":["https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db","https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3","https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b","https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a","https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-22T16:41:11.231219466+00:00"},"epss":{"cve":"CVE-2026-63887","score":0.00778,"percentile":0.55574,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}