CVE-2026-48685

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.

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Produits concernés

• Pavel-odintsov fastnetmon

Scores CVSS

Faiblesses (CWE)

• CWE-130

Références

• 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

Ailleurs

• NVD
• CVE.org
• CIRCL Vulnerability-Lookup
• CERT-FR
• GitHub Advisories