GHSA-F762-5MRW-32X8

Vulnerability from github – Published: 2026-05-26 18:31 – Updated: 2026-05-26 21:31
VLAI
Details

FastNetMon Community Edition through 1.2.9 is vulnerable to a local symlink attack via predictable file paths in /tmp. The statistics file path defaults to '/tmp/fastnetmon.dat' (src/fastnetmon.cpp line 159). The print_screen_contents_into_file() function (src/fastnetmon_logic.cpp line 2186) opens this path with std::ios::trunc without checking for symlinks or using O_NOFOLLOW. Additionally, the chmod() call on line 2190 always operates on cli_stats_file_path regardless of which file_path parameter was passed (a bug that applies wrong permissions), and the umask is set to 0 during daemonization (src/fastnetmon.cpp line 1821), making all created files world-writable. A local attacker can exploit this to overwrite arbitrary files as the FastNetMon process user (typically root).

Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
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{
  "affected": [],
  "aliases": [
    "CVE-2026-48693"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-59"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-26T17:16:53Z",
    "severity": "MODERATE"
  },
  "details": "FastNetMon Community Edition through 1.2.9 is vulnerable to a local symlink attack via predictable file paths in /tmp. The statistics file path defaults to \u0027/tmp/fastnetmon.dat\u0027 (src/fastnetmon.cpp line 159). The print_screen_contents_into_file() function (src/fastnetmon_logic.cpp line 2186) opens this path with std::ios::trunc without checking for symlinks or using O_NOFOLLOW. Additionally, the chmod() call on line 2190 always operates on cli_stats_file_path regardless of which file_path parameter was passed (a bug that applies wrong permissions), and the umask is set to 0 during daemonization (src/fastnetmon.cpp line 1821), making all created files world-writable. A local attacker can exploit this to overwrite arbitrary files as the FastNetMon process user (typically root).",
  "id": "GHSA-f762-5mrw-32x8",
  "modified": "2026-05-26T21:31:57Z",
  "published": "2026-05-26T18:31:47Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48693"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pavel-odintsov/fastnetmon"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pavel-odintsov/fastnetmon/blob/master/src/fastnetmon.cpp"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pavel-odintsov/fastnetmon/blob/master/src/fastnetmon_logic.cpp"
    },
    {
      "type": "WEB",
      "url": "https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48693-symlink-tmp"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}


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