fastnetmon — security advisory
FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_object_ptr, memcpy_from_ptr, memcpy_from_object_ptr) use an incorrect bounds check of the form 'if (offset + length > maximum_internal_storage_size + 1)' instead of the correct 'if (offset + length > maximum_internal_storage_size)'. This allows writing exactly one byte past the end of the heap-allocated buffer. The class is used pervasively in BGP message encoding/decoding, NetFlow template processing, and Flow Spec NLRI construction. An attacker who can send network traffic (NetFlow, sFlow, IPFIX, or BGP) to a FastNetMon instance can trigger this overflow, potentially achieving arbitrary code execution by corrupting heap metadata. Notably, the append_byte() method uses the correct bounds check, confirming the inconsistency.
- 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-2026-48689
- 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 off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_object_ptr, memcpy_from_ptr, memcpy_from_object_ptr) use an incorrect bounds check of the form 'if (offset + length > maximum_internal_storage_size + 1)' instead of the correct 'if (offset + length > maximum_internal_storage_size)'. This allows writing exactly one byte past the end of the heap-allocated buffer. The class is used pervasively in BGP message encoding/decoding, NetFlow template processing, and Flow Spec NLRI construction. An attacker who can send network traffic (NetFlow, sFlow, IPFIX, or BGP) to a FastNetMon instance can trigger this overflow, potentially achieving arbitrary code execution by corrupting heap metadata. Notably, the append_byte() method uses the correct bounds check, confirming the inconsistency.
osv:UBUNTU-CVE-2026-48689
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": "2fb5750a71482384be899d18d96f23b72fe8b47ae2bc3e6e924757b5648a9255",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-48689",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-48689",
"summary": "FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_object_ptr, memcpy_from_ptr, memcpy_from_object_ptr) use an incorrect bounds check of the form 'if (offset + length > maximum_internal_storage_size + 1)' instead of the correct 'if (offset + length > maximum_internal_storage_size)'. This allows writing exactly one byte past the end of the heap-allocated buffer. The class is used pervasively in BGP message encoding/decoding, NetFlow template processing, and Flow Spec NLRI construction. An attacker who can send network traffic (NetFlow, sFlow, IPFIX, or BGP) to a FastNetMon instance can trigger this overflow, potentially achieving arbitrary code execution by corrupting heap metadata. Notably, the append_byte() method uses the correct bounds check, confirming the inconsistency.",
"evidence": "osv:UBUNTU-CVE-2026-48689",
"products": [
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"prerequisites": [],
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{
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{
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"evidence": "/affected/2/versions"
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{
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"evidence": "/affected/2/versions"
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{
"value": "1.2.9-1build1",
"evidence": "/affected/2/versions"
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{
"value": "1.2.9-1build2",
"evidence": "/affected/2/versions"
}
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{
"name": {
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"affected_versions": [
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{
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{
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],
"severity": "critical",
"structured": {
"id": "UBUNTU-CVE-2026-48689",
"aliases": [
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],
"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:H/I:H/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
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"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
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{
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],
"package": {
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"purl": "pkg:deb/ubuntu/fastnetmon?arch=source&distro=esm-apps%2Fnoble",
"ecosystem": "Ubuntu:Pro:24.04:LTS"
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"versions": [
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"1.2.6-1",
"1.2.6-1build1",
"1.2.6-1build2",
"1.2.6-1build3",
"1.2.6-1build4"
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"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48689.json"
},
"ecosystem_specific": {
"binaries": [
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"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
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{
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"package": {
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"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"
],
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}
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{
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"ecosystem": "Ubuntu:26.10"
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"versions": [
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"1.2.9-1",
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"ecosystem_specific": {
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],
"package": {
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"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-2026-48689.json"
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"ecosystem_specific": {
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{
"binary_name": "fastnetmon",
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"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
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}
],
"modified": "2026-10-17T12:58:30.328974241Z",
"provider": "osv",
"upstream": [
"CVE-2026-48689"
],
"references": [
"https://ubuntu.com/security/CVE-2026-48689",
"https://www.cve.org/CVERecord?id=CVE-2026-48689",
"https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48689-dynamic-buffer-off-by-one",
"https://github.com/pavel-odintsov/fastnetmon/pull/1051",
"https://github.com/pavel-odintsov/fastnetmon/commit/fa80390ed446f887ca6fa39c9e5b6fff8846e822",
"https://github.com/pavel-odintsov/fastnetmon",
"https://github.com/pavel-odintsov/fastnetmon/blob/master/src/dynamic_binary_buffer.hpp",
"https://ubuntu.com/security/notices/USN-8429-1"
]
},
"related_cves": [
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"value": "CVE-2026-48689",
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],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 358674,
"published_at": "2026-05-26T19:16:00+00:00"
}