CVE-2026-48691

FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder

High · published May 26, 2026

CVSS v3.1
7.3
EPSS
1%
Percentile
46.5
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.3 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
CVSS v4.0
Not supplied
EPSS
0.00571 · 46.5th percentile
Published
2026-05-26T00:00Z
EPSS history
Timeline
  • 26 MAY 00:00Z
    FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder
    cvelistv5