CriticalFix available
fastnetmon — security advisory
FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.
- Products
- fastnetmon
- Affected 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, 1.2.8+git20250911-1, 1.2.8+git20250911-1build1, 1.2.8+git20250911-1build2, 1.2.8+git20250911-2, 1.2.8-1build1, 1.2.8-1build2, 1.2.9-1, 1.2.9-1build1, 1.2.9-1build2
- Fixed versions
- 1.2.6-1ubuntu0.1~esm1, 1.2.8+git20250911-2ubuntu0.1~esm1
- CVEs
- CVE-2026-48691
- 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 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.
osv:UBUNTU-CVE-2026-48691
fastnetmon
Fixed versions: 1.2.6-1ubuntu0.1~esm1
fastnetmon
Fixed versions: Not specified
fastnetmon
Fixed versions: Not specified
fastnetmon
Fixed versions: 1.2.8+git20250911-2ubuntu0.1~esm1
Complete source record
{
"id": "1d753e1e026f3a7df7fa5941787e192f2abef02fb431e5fa114c67497d7517b6",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-48691",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-48691",
"summary": "FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.",
"evidence": "osv:UBUNTU-CVE-2026-48691",
"products": [
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1.2.6-1ubuntu0.1~esm1",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": [
{
"value": "1.2.5-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.2.6-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.2.6-1build1",
"evidence": "/affected/0/versions"
},
{
"value": "1.2.6-1build2",
"evidence": "/affected/0/versions"
},
{
"value": "1.2.6-1build3",
"evidence": "/affected/0/versions"
},
{
"value": "1.2.6-1build4",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.2.8-1build1",
"evidence": "/affected/1/versions"
},
{
"value": "1.2.8-1build2",
"evidence": "/affected/1/versions"
},
{
"value": "1.2.8+git20250911-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.2.8+git20250911-2",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.9-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.9-1build1",
"evidence": "/affected/2/versions"
},
{
"value": "1.2.9-1build2",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
"value": "fastnetmon",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1.2.8+git20250911-2ubuntu0.1~esm1",
"evidence": "/affected/3/ranges"
}
],
"affected_versions": [
{
"value": "1.2.8+git20250911-1",
"evidence": "/affected/3/versions"
},
{
"value": "1.2.8+git20250911-1build1",
"evidence": "/affected/3/versions"
},
{
"value": "1.2.8+git20250911-1build2",
"evidence": "/affected/3/versions"
},
{
"value": "1.2.8+git20250911-2",
"evidence": "/affected/3/versions"
}
]
}
],
"severity": "critical",
"structured": {
"id": "UBUNTU-CVE-2026-48691",
"aliases": [
"UBUNTU-CVE-2026-48691"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.2.6-1ubuntu0.1~esm1"
}
]
}
],
"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"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48691.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.2.6-1ubuntu0.1~esm1"
}
],
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
}
},
{
"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-2026-48691.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-2026-48691.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.2.9-1build2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.2.8+git20250911-2ubuntu0.1~esm1"
}
]
}
],
"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"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48691.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "fastnetmon",
"binary_version": "1.2.8+git20250911-2ubuntu0.1~esm1"
}
],
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
}
}
],
"modified": "2026-10-17T12:58:31.034054842Z",
"provider": "osv",
"upstream": [
"CVE-2026-48691"
],
"references": [
"https://ubuntu.com/security/CVE-2026-48691",
"https://www.cve.org/CVERecord?id=CVE-2026-48691",
"https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflow",
"https://github.com/pavel-odintsov/fastnetmon/commit/94c66d5b100c42fb8bd10a22ca595e46895d60d0",
"https://github.com/pavel-odintsov/fastnetmon/pull/1054",
"https://github.com/pavel-odintsov/fastnetmon",
"https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hpp",
"https://ubuntu.com/security/notices/USN-8429-1"
]
},
"related_cves": [
{
"value": "CVE-2026-48691",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 358683,
"published_at": "2026-05-26T17:16:00+00:00"
}