Vulnerability Description
FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_object_ptr, memcpy_from_ptr, memcpy_from_object_ptr) use an incorrect bounds check of the form 'if (offset + length > maximum_internal_storage_size + 1)' instead of the correct 'if (offset + length > maximum_internal_storage_size)'. This allows writing exactly one byte past the end of the heap-allocated buffer. The class is used pervasively in BGP message encoding/decoding, NetFlow template processing, and Flow Spec NLRI construction. An attacker who can send network traffic (NetFlow, sFlow, IPFIX, or BGP) to a FastNetMon instance can trigger this overflow, potentially achieving arbitrary code execution by corrupting heap metadata. Notably, the append_byte() method uses the correct bounds check, confirming the inconsistency.
CVSS Score
CRITICAL
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/dynamic_binary_buffProduct
- https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48689-dynamic-buffer-off-bExploitThird Party Advisory
FAQ
What is CVE-2026-48689?
CVE-2026-48689 is a vulnerability with a CVSS score of 9.8 (CRITICAL). FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, ...
How severe is CVE-2026-48689?
CVE-2026-48689 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-48689?
Check the references section above for vendor advisories and patch information. Affected products include: Pavel-Odintsov Fastnetmon.