Vulnerability Details CVE-2026-48689
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 9.2%
CVSS Severity
CVSS v3 Score 9.8
References
Products affected by CVE-2026-48689
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.0.0
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.0
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.1
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.2
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.3
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.4
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.5
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.6
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.7
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.8
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.1.9
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.0
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.1
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.2
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.3
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.4
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.5
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.6
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.7
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cpe:2.3:a:pavel-odintsov:fastnetmon:1.2.8