{"id":"CVE-2026-63887","title":"scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf","summary":"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-byt…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < cb84e974fb172bc71386289f37b78ea679410b39","Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < b19382dfc6e7dee6d3859ba44b6ca29e97a51627","Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < efe633e600a0ac68357206fede21b1ac8178f3b8","Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 4e9f0c4a645c995bc75c06c7b3644254ffb4c76b","Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 30bf335e8fe170322080ee001f05ca29c50680b3","Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 594a40360012ce5f94c715d5e3b20fa3af7d525a","Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 26e4a304b7e6f1338c675d527608d32549c091db","Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < bf33e01f88388c43e285492a63e539df6ffed64c","Linux 3.1"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T15:32:57.099055Z"},"published":"2026-07-19","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:42:10.168Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63887","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"}],"tags":["cve.org"],"epss":0.00778,"epssPercentile":0.54971,"ingestedAt":"2026-10-16T17:24:46.773Z","slug":"CVE-2026-63887","body":"## Overview\n\nIn 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.)\n\n## Affected\n\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < cb84e974fb172bc71386289f37b78ea679410b39`\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < b19382dfc6e7dee6d3859ba44b6ca29e97a51627`\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < efe633e600a0ac68357206fede21b1ac8178f3b8`\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 4e9f0c4a645c995bc75c06c7b3644254ffb4c76b`\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 30bf335e8fe170322080ee001f05ca29c50680b3`\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 594a40360012ce5f94c715d5e3b20fa3af7d525a`\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < 26e4a304b7e6f1338c675d527608d32549c091db`\n- `Linux >= e48354ce078c079996f89d715dfa44814b4eba01 < bf33e01f88388c43e285492a63e539df6ffed64c`\n- `Linux 3.1`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}