CVE-2026-48685

NameCVE-2026-48685
DescriptionFastNetMon Community Edition through 1.2.9 has out-of-bounds memory access because it incorrectly parses BGP path attributes with the extended length flag set. In src/bgp_protocol.hpp, the parse_raw_bgp_attribute() function correctly identifies when extended_length_bit is set and sets length_of_length_field to 2, but then reads only a single byte for the attribute value length (attribute_value_length = value[2] at line 173). Per RFC 4271 Section 4.3, when the Extended Length bit is set, the Attribute Length field is two octets and the value should be read as a 16-bit big-endian integer from value[2] and value[3]. As a result, any attribute longer than 255 bytes has its length silently truncated to the low byte (e.g., 300 bytes = 0x012C is read as 0x2C = 44 bytes). The remaining 256 bytes are then misinterpreted as subsequent attributes, causing cascading parse failures and potential out-of-bounds memory access.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs1138646

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
fastnetmon (PTS)bookworm, bookworm (security)1.2.4-2+deb12u1vulnerable
trixie1.2.8-1vulnerable
forky, sid1.2.9-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
fastnetmonsource(unstable)1.2.9-1unimportant1138646

Notes

https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48685-bgp-extended-length
Not a vulnerability, at best an interop issue
https://github.com/pavel-odintsov/fastnetmon/commit/2bf813b2590b9847308877a65fc72df560dd282f (v1.2.9)

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