CVE-2026-48685
FastNetMon BGP Path Attribute Out-of-Bounds Memory Access Vulnerability
Description
FastNetMon Community Edition through 1.2.9 has out-of-bounds memory access because it incorrectly parses BGP path attributes with the extended length flag set. In src/bgp_protocol.hpp, the parse_raw_bgp_attribute() function correctly identifies when extended_length_bit is set and sets length_of_length_field to 2, but then reads only a single byte for the attribute value length (attribute_value_length = value[2] at line 173). Per RFC 4271 Section 4.3, when the Extended Length bit is set, the Attribute Length field is two octets and the value should be read as a 16-bit big-endian integer from value[2] and value[3]. As a result, any attribute longer than 255 bytes has its length silently truncated to the low byte (e.g., 300 bytes = 0x012C is read as 0x2C = 44 bytes). The remaining 256 bytes are then misinterpreted as subsequent attributes, causing cascading parse failures and potential out-of-bounds memory access.
INFO
Published Date :
May 26, 2026, 4:16 p.m.
Last Modified :
July 24, 2026, 11:10 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update FastNetMon Community Edition to a version later than 1.2.9.
- Apply vendor patches or security updates.
- Verify BGP parsing logic for extended length attributes.
- Review secure coding practices for network protocols.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-48685.
| URL | Resource |
|---|---|
| https://github.com/pavel-odintsov/fastnetmon | Product |
| https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hpp | Product |
| https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48685-bgp-extended-length | Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-48685 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-48685
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-48685 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-48685 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Jul. 24, 2026
Action Type Old Value New Value Added Translation Title: FastNetMon Community Edition, Description: FastNetMon Community Edition hasta la versión 1.2.9 tiene acceso a memoria fuera de límites porque analiza incorrectamente los atributos de ruta BGP con el indicador de longitud extendida activado. En src/bgp_protocol.hpp, la función parse_raw_bgp_attribute() identifica correctamente cuando extended_length_bit está activado y establece length_of_length_field en 2, pero luego lee solo un byte para la longitud del valor del atributo (attribute_value_length = value[2] en la línea 173). Según la RFC 4271 Sección 4.3, cuando el bit de longitud extendida está activado, el campo de longitud del atributo es de dos octetos y el valor debe leerse como un entero big-endian de 16 bits de value[2] y value[3]. Como resultado, cualquier atributo de más de 255 bytes tiene su longitud truncada silenciosamente al byte bajo (por ejemplo, 300 bytes = 0x012C se lee como 0x2C = 44 bytes). Los 256 bytes restantes son luego malinterpretados como atributos subsiguientes, causando fallos de análisis en cascada y potencial acceso a memoria fuera de límites. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'n/a', 'product': 'n/a', 'versions': [{'status': 'affected', 'version': 'n/a'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-48685', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-05-26T20:56:09.270143Z'} -
Initial Analysis by [email protected]
May. 27, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:pavel-odintsov:fastnetmon:*:*:*:*:community:*:*:* versions up to (including) 1.2.9 Added Reference Type MITRE: https://github.com/pavel-odintsov/fastnetmon Types: Product Added Reference Type MITRE: https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hpp Types: Product Added Reference Type MITRE: https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48685-bgp-extended-length Types: Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 26, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-130 -
New CVE Received by [email protected]
May. 26, 2026
Action Type Old Value New Value Added Description FastNetMon Community Edition through 1.2.9 has out-of-bounds memory access because it incorrectly parses BGP path attributes with the extended length flag set. In src/bgp_protocol.hpp, the parse_raw_bgp_attribute() function correctly identifies when extended_length_bit is set and sets length_of_length_field to 2, but then reads only a single byte for the attribute value length (attribute_value_length = value[2] at line 173). Per RFC 4271 Section 4.3, when the Extended Length bit is set, the Attribute Length field is two octets and the value should be read as a 16-bit big-endian integer from value[2] and value[3]. As a result, any attribute longer than 255 bytes has its length silently truncated to the low byte (e.g., 300 bytes = 0x012C is read as 0x2C = 44 bytes). The remaining 256 bytes are then misinterpreted as subsequent attributes, causing cascading parse failures and potential out-of-bounds memory access. Added Reference https://github.com/pavel-odintsov/fastnetmon Added Reference https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hpp Added Reference https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48685-bgp-extended-length