CVE-2026-48691
criticalpriority · track · 39EPSS 0.003 · 24 %ileEUUSEPSS · scored 2026-10-28
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 7.3–9.8
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
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affected products (2)
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also known as (3)
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sources
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references (9)
External citations — patches, advisories, analysis.
- https://github.com/pavel-odintsov/fastnetmoncnnvd
- https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hppcnnvd
- https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflowcnnvd
- https://github.com/pavel-odintsov/fastnetmonenisa_euvd
- https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hppenisa_euvd
- https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflowenisa_euvd
- https://github.com/pavel-odintsov/fastnetmonProductnvd
- https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hppProductnvd
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