| Name | CVE-2026-48689 |
| 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. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DSA-6375-1 |
| Debian Bugs | 1138646 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| fastnetmon (PTS) | bookworm, bookworm (security) | 1.2.4-2+deb12u1 | fixed |
| trixie (security), trixie | 1.2.9-0+deb13u1 | fixed | |
| forky, sid | 1.2.9-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| fastnetmon | source | bullseye | (not affected) | |||
| fastnetmon | source | bookworm | (not affected) | |||
| fastnetmon | source | trixie | 1.2.9-0+deb13u1 | DSA-6375-1 | ||
| fastnetmon | source | (unstable) | 1.2.9-1 | 1138646 |
[bookworm] - fastnetmon <not-affected> (Vulnerable code introduced later)
[bullseye] - fastnetmon <not-affected> (Vulnerable code introduced later)
https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48689-dynamic-buffer-off-by-one
https://github.com/pavel-odintsov/fastnetmon/pull/1051
Fixed by: https://github.com/pavel-odintsov/fastnetmon/commit/fa80390ed446f887ca6fa39c9e5b6fff8846e822 (v1.2.9)
Introduced by: https://github.com/pavel-odintsov/fastnetmon/commit/7836db2091522831c703c5a9dc3f39be9f12def5 (v1.2.6)