CVE-2026-48689
Publication date 26 May 2026
Last updated 27 May 2026
Ubuntu priority
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| fastnetmon | 26.04 LTS resolute |
Needs evaluation
|
| 25.10 questing |
Needs evaluation
|
|
| 24.04 LTS noble |
Needs evaluation
|
|
| 22.04 LTS jammy | Not in release | |
| 20.04 LTS focal |
Needs evaluation
|
|
| 18.04 LTS bionic |
Needs evaluation
|
Severity score breakdown
CVSS version: CVSS v3.0
Base score
9.8 · Critical
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
Other references
- https://www.cve.org/CVERecord?id=CVE-2026-48689
- https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48689-dynamic-buffer-off-by-one
- https://github.com/pavel-odintsov/fastnetmon/pull/1051
- https://github.com/pavel-odintsov/fastnetmon/commit/fa80390ed446f887ca6fa39c9e5b6fff8846e822
- https://github.com/pavel-odintsov/fastnetmon
- https://github.com/pavel-odintsov/fastnetmon/blob/master/src/dynamic_binary_buffer.hpp