{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "e48354ce078c079996f89d715dfa44814b4eba01"
            },
            {
              "fixed": "cb84e974fb172bc71386289f37b78ea679410b39"
            },
            {
              "fixed": "b19382dfc6e7dee6d3859ba44b6ca29e97a51627"
            },
            {
              "fixed": "efe633e600a0ac68357206fede21b1ac8178f3b8"
            },
            {
              "fixed": "4e9f0c4a645c995bc75c06c7b3644254ffb4c76b"
            },
            {
              "fixed": "30bf335e8fe170322080ee001f05ca29c50680b3"
            },
            {
              "fixed": "594a40360012ce5f94c715d5e3b20fa3af7d525a"
            },
            {
              "fixed": "26e4a304b7e6f1338c675d527608d32549c091db"
            },
            {
              "fixed": "bf33e01f88388c43e285492a63e539df6ffed64c"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.1.0"
            },
            {
              "fixed": "5.10.259"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.11.0"
            },
            {
              "fixed": "5.15.210"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.16.0"
            },
            {
              "fixed": "6.1.176"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.2.0"
            },
            {
              "fixed": "6.6.143"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.93"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.35"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.0.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63887.json"
  },
  "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-\u003ersp_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-\u003ekey, er-\u003evalue);\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.)",
  "id": "CVE-2026-63887",
  "modified": "2026-07-21T03:42:05.410321827Z",
  "published": "2026-07-19T14:55:00.114Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/26e4a304b7e6f1338c675d527608d32549c091db"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/30bf335e8fe170322080ee001f05ca29c50680b3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4e9f0c4a645c995bc75c06c7b3644254ffb4c76b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/594a40360012ce5f94c715d5e3b20fa3af7d525a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b19382dfc6e7dee6d3859ba44b6ca29e97a51627"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bf33e01f88388c43e285492a63e539df6ffed64c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cb84e974fb172bc71386289f37b78ea679410b39"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/efe633e600a0ac68357206fede21b1ac8178f3b8"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63887.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63887"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf"
}