CVE-2026-48686
CriticalSummary
FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI decoder. The function decode_bgp_subnet_encoding_ipv4_raw() does not validate the prefix length, leading to potential arbitrary code execution.
Risk Assessment
Stack buffer overflow can be exploited for arbitrary code execution, posing a serious threat to the security of the system and the organization's data.
Recommendation
It is recommended to upgrade to the latest version of FastNetMon to mitigate this vulnerability and implement additional input validation mechanisms.
Original NVD description (English source)
FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI (Network Layer Reachability Information) decoder. The function decode_bgp_subnet_encoding_ipv4_raw() in src/bgp_protocol.cpp reads prefix_bit_length directly from the BGP packet (line 99) without validating it is <= 32 for IPv4 prefixes. This value is passed to how_much_bytes_we_need_for_storing_certain_subnet_mask() which computes ceil(prefix_bit_length / 8), returning up to 32 bytes for a prefix_bit_length of 255. The result is used as the length argument to memcpy() (line 106), which copies into a 4-byte uint32_t stack variable (prefix_ipv4). This causes a stack buffer overflow of up to 28 bytes, which can be exploited for arbitrary code execution. Additionally, the unvalidated prefix_bit_length is passed to convert_cidr_to_binary_netmask_local_function_copy() (line 111), where a shift of (32 - cidr) with cidr > 32 causes undefined behavior.