CVE-2026-48691
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk23th percentile - higher than 23% of all known CVEs
Summary
Integer overflow in FastNetMon Community Edition up to 1.2.9 in the BGP AS_PATH attribute encoder leads to a heap buffer overflow.
Risk Assessment
An attacker can remotely cause a crash or potentially take over the system by sending a crafted BGP message.
Recommendation
Update FastNetMon to a version above 1.2.9 or apply a patch limiting AS_PATH length.
Original NVD description (English source)
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.