{
  "schema_version": "1.5.0",
  "id": "CURL-CVE-2018-1000120",
  "aliases": [
    "CVE-2018-1000120"
  ],
  "summary": "FTP path trickery leads to NIL byte out of bounds write",
  "modified": "2026-04-25T17:48:46.00Z",
  "database_specific": {
    "package": "curl",
    "affects": "both",
    "URL": "https://curl.se/docs/CVE-2018-1000120.json",
    "www": "https://curl.se/docs/CVE-2018-1000120.html",
    "CWE": {
      "id": "CWE-122",
      "desc": "Heap-based Buffer Overflow"
    },
    "last_affected": "7.58.0",
    "severity": "High"
  },
  "published": "2018-03-14T08:00:00.00Z",
  "affected": [
    {
      "ranges": [
        {
           "type": "SEMVER",
           "events": [
             {"introduced": "7.12.3"},
             {"fixed": "7.59.0"}
           ]
        },
        {
           "type": "GIT",
           "repo": "https://github.com/curl/curl.git",
           "events": [
             {"introduced": "6e1e9caa32da099569bb95e64faf0b5f3cf103b5"},
             {"fixed": "535432c0adb62fe167ec09621500470b6fa4eb0f"}
           ]
        }
      ],
      "versions": [
        "7.58.0", "7.57.0", "7.56.1", "7.56.0", "7.55.1", "7.55.0", "7.54.1", 
        "7.54.0", "7.53.1", "7.53.0", "7.52.1", "7.52.0", "7.51.0", "7.50.3", 
        "7.50.2", "7.50.1", "7.50.0", "7.49.1", "7.49.0", "7.48.0", "7.47.1", 
        "7.47.0", "7.46.0", "7.45.0", "7.44.0", "7.43.0", "7.42.1", "7.42.0", 
        "7.41.0", "7.40.0", "7.39.0", "7.38.0", "7.37.1", "7.37.0", "7.36.0", 
        "7.35.0", "7.34.0", "7.33.0", "7.32.0", "7.31.0", "7.30.0", "7.29.0", 
        "7.28.1", "7.28.0", "7.27.0", "7.26.0", "7.25.0", "7.24.0", "7.23.1", 
        "7.23.0", "7.22.0", "7.21.7", "7.21.6", "7.21.5", "7.21.4", "7.21.3", 
        "7.21.2", "7.21.1", "7.21.0", "7.20.1", "7.20.0", "7.19.7", "7.19.6", 
        "7.19.5", "7.19.4", "7.19.3", "7.19.2", "7.19.1", "7.19.0", "7.18.2", 
        "7.18.1", "7.18.0", "7.17.1", "7.17.0", "7.16.4", "7.16.3", "7.16.2", 
        "7.16.1", "7.16.0", "7.15.5", "7.15.4", "7.15.3", "7.15.2", "7.15.1", 
        "7.15.0", "7.14.1", "7.14.0", "7.13.2", "7.13.1", "7.13.0", "7.12.3"
      ]
    }
  ],
  "credits": [
    {
      "name": "Duy Phan Thanh",
      "type": "FINDER"
    },
    {
      "name": "Daniel Stenberg",
      "type": "REMEDIATION_DEVELOPER"
    }
  ],
  "details": "curl can be fooled into writing a zero byte out of bounds.\n\nThis bug can trigger when curl is told to work on an FTP URL, with the setting\nto only issue a single CWD command (`--ftp-method singlecwd` or the libcurl\nalternative `CURLOPT_FTP_FILEMETHOD`).\n\ncurl then URL-decodes the given path, calls strlen() on the result and deducts\nthe length of the filename part to find the end of the directory within the\nbuffer. It then writes a zero byte on that index, in a buffer allocated on the\nheap.\n\nIf the directory part of the URL contains a \"%00\" sequence, the directory\nlength might end up shorter than the filename path, making the calculation\n`size_t index = directory_len - filepart_len` end up with a huge index\nvariable for where the zero byte gets stored: `heap_buffer[index] = 0`. On\nseveral architectures that huge index wraps and works as a negative value,\nthus overwriting memory *before* the intended heap buffer.\n\nBy using different file part lengths and putting %00 in different places in\nthe URL, an attacker that can control what paths a curl-using application uses\ncan write that zero byte on different indexes."
}