CVE-2026-48686
Description
FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI (Network Layer Reachability Information) decoder. The function decode_bgp_subnet_encoding_ipv4_raw() in src/bgp_protocol.cpp reads prefix_bit_length directly from the BGP packet (line 99) without validating it is <= 32 for IPv4 prefixes. This value is passed to how_much_bytes_we_need_for_storing_certain_subnet_mask() which computes ceil(prefix_bit_length / 8), returning up to 32 bytes for a prefix_bit_length of 255. The result is used as the length argument to memcpy() (line 106), which copies into a 4-byte uint32_t stack variable (prefix_ipv4). This causes a stack buffer overflow of up to 28 bytes, which can be exploited for arbitrary code execution. Additionally, the unvalidated prefix_bit_length is passed to convert_cidr_to_binary_netmask_local_function_copy() (line 111), where a shift of (32 - cidr) with cidr > 32 causes undefined behavior.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
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OS impact
Debian Mixed 4 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Affected | — |
| sid | Fixed | 1.2.9-1 |
| forky | Affected | — |
| bookworm | Affected | — |
Application impact
| Vendor | Product | Versions | Fixed |
|---|---|---|---|
| pavel-odintsov | fastnetmon | {"endIncluding":"1.2.9"} | |
References
CWEs
CWE-120 CWE-787
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.