CVE-2026-48691

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.

• CWE-190
• CWE-122
• CWE-190

• https://github.com/pavel-odintsov/fastnetmonProduct
• https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hppProduct
• https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflowThird Party Advisory

Published

May 26, 2026

Last Modified

Jul 24, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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