Medium
fastnetmon — security advisory
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).
- Products
- fastnetmon
- Affected versions
- 1.1.3+dfsg-3, 1.1.3+dfsg-4, 1.1.3+dfsg-6build1, 1.1.4-1, 1.1.4-1build3, 1.1.4-1build4, 1.1.4-1build5, 1.1.4-1ubuntu0.1~esm1, 1.2.5-1, 1.2.6-1, 1.2.6-1build1, 1.2.6-1build2, 1.2.6-1build3, 1.2.6-1build4, 1.2.6-1ubuntu0.1~esm1, 1.2.8+git20250911-1, 1.2.8+git20250911-1build1, 1.2.8+git20250911-1build2, 1.2.8+git20250911-2, 1.2.8+git20250911-2ubuntu0.1~esm1, 1.2.8-1build1, 1.2.8-1build2, 1.2.9-1, 1.2.9-1build1, 1.2.9-1build2
- Fixed versions
- Not specified
- CVEs
- CVE-2026-48693
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:21 UTC · Revision 1
Source evidence
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).
osv:UBUNTU-CVE-2026-48693
fastnetmon
Fixed versions: Not specified
fastnetmon
Fixed versions: Not specified
fastnetmon
Fixed versions: Not specified
fastnetmon
Fixed versions: Not specified
fastnetmon
Fixed versions: Not specified
fastnetmon
Fixed versions: Not specified
Complete source record
{
"id": "311d093d80246754f3ff765cf4c220d4f6b857c75189d16bec5f329b3861ed1d",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-48693",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-48693",
"summary": "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).",
"evidence": "osv:UBUNTU-CVE-2026-48693",
"products": [
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.1.3+dfsg-3",
"evidence": "/affected/0/versions"
},
{
"value": "1.1.3+dfsg-4",
"evidence": "/affected/0/versions"
},
{
"value": "1.1.3+dfsg-6build1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.1.4-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.1.4-1build3",
"evidence": "/affected/1/versions"
},
{
"value": "1.1.4-1build4",
"evidence": "/affected/1/versions"
},
{
"value": "1.1.4-1build5",
"evidence": "/affected/1/versions"
},
{
"value": "1.1.4-1ubuntu0.1~esm1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.2.5-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.6-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.6-1build1",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.6-1build2",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.6-1build3",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.6-1build4",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.6-1ubuntu0.1~esm1",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.2.8-1build1",
"evidence": "/affected/3/versions"
},
{
"value": "1.2.8-1build2",
"evidence": "/affected/3/versions"
},
{
"value": "1.2.8+git20250911-1",
"evidence": "/affected/3/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.2.8+git20250911-2",
"evidence": "/affected/4/versions"
},
{
"value": "1.2.9-1",
"evidence": "/affected/4/versions"
},
{
"value": "1.2.9-1build1",
"evidence": "/affected/4/versions"
},
{
"value": "1.2.9-1build2",
"evidence": "/affected/4/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.2.8+git20250911-1",
"evidence": "/affected/5/versions"
},
{
"value": "1.2.8+git20250911-1build1",
"evidence": "/affected/5/versions"
},
{
"value": "1.2.8+git20250911-1build2",
"evidence": "/affected/5/versions"
},
{
"value": "1.2.8+git20250911-2",
"evidence": "/affected/5/versions"
},
{
"value": "1.2.8+git20250911-2ubuntu0.1~esm1",
"evidence": "/affected/5/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "UBUNTU-CVE-2026-48693",
"aliases": [
"UBUNTU-CVE-2026-48693"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "fastnetmon",
"purl": "pkg:deb/ubuntu/fastnetmon?arch=source&distro=bionic",
"ecosystem": "Ubuntu:18.04:LTS"
},
"versions": [
"1.1.3+dfsg-3",
"1.1.3+dfsg-4",
"1.1.3+dfsg-6build1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48693.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.1.3+dfsg-6build1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "fastnetmon",
"purl": "pkg:deb/ubuntu/fastnetmon?arch=source&distro=esm-apps%2Ffocal",
"ecosystem": "Ubuntu:Pro:20.04:LTS"
},
"versions": [
"1.1.4-1",
"1.1.4-1build3",
"1.1.4-1build4",
"1.1.4-1build5",
"1.1.4-1ubuntu0.1~esm1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48693.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.1.4-1ubuntu0.1~esm1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "fastnetmon",
"purl": "pkg:deb/ubuntu/fastnetmon?arch=source&distro=esm-apps%2Fnoble",
"ecosystem": "Ubuntu:Pro:24.04:LTS"
},
"versions": [
"1.2.5-1",
"1.2.6-1",
"1.2.6-1build1",
"1.2.6-1build2",
"1.2.6-1build3",
"1.2.6-1build4",
"1.2.6-1ubuntu0.1~esm1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48693.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.2.6-1ubuntu0.1~esm1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "fastnetmon",
"purl": "pkg:deb/ubuntu/fastnetmon?arch=source&distro=questing",
"ecosystem": "Ubuntu:25.10"
},
"versions": [
"1.2.8-1build1",
"1.2.8-1build2",
"1.2.8+git20250911-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48693.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.2.8+git20250911-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "fastnetmon",
"purl": "pkg:deb/ubuntu/fastnetmon?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"1.2.8+git20250911-2",
"1.2.9-1",
"1.2.9-1build1",
"1.2.9-1build2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48693.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.2.9-1build2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "fastnetmon",
"purl": "pkg:deb/ubuntu/fastnetmon?arch=source&distro=esm-apps%2Fresolute",
"ecosystem": "Ubuntu:Pro:26.04:LTS"
},
"versions": [
"1.2.8+git20250911-1",
"1.2.8+git20250911-1build1",
"1.2.8+git20250911-1build2",
"1.2.8+git20250911-2",
"1.2.8+git20250911-2ubuntu0.1~esm1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48693.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.2.8+git20250911-2ubuntu0.1~esm1"
}
]
}
}
],
"modified": "2026-10-17T12:58:31.128720746Z",
"provider": "osv",
"upstream": [
"CVE-2026-48693"
],
"references": [
"https://ubuntu.com/security/CVE-2026-48693",
"https://www.cve.org/CVERecord?id=CVE-2026-48693",
"https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48693-symlink-tmp",
"https://github.com/pavel-odintsov/fastnetmon",
"https://github.com/pavel-odintsov/fastnetmon/blob/master/src/fastnetmon.cpp",
"https://github.com/pavel-odintsov/fastnetmon/blob/master/src/fastnetmon_logic.cpp"
]
},
"related_cves": [
{
"value": "CVE-2026-48693",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 358685,
"published_at": "2026-05-26T17:16:00+00:00"
}