Vulnerability Description
FastNetMon 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Pavel-Odintsov | Fastnetmon | <= 1.2.9 |
Related Weaknesses (CWE)
References
- https://github.com/pavel-odintsov/fastnetmonProduct
- https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hppProduct
- https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48685-bgp-extended-lengthThird Party Advisory
FAQ
What is CVE-2026-48685?
CVE-2026-48685 is a vulnerability with a CVSS score of 6.5 (MEDIUM). FastNetMon 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_b...
How severe is CVE-2026-48685?
CVE-2026-48685 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-48685?
Check the references section above for vendor advisories and patch information. Affected products include: Pavel-Odintsov Fastnetmon.