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How the mentioned CVE works:
In FastNetMon Community Edition through 1.2.9, the function `allocate_buffer()` inside `src/packet_storage.hpp` computes memory allocation using 32-bit unsigned integer multiplication: memory_size_in_bytes = buffer_size_in_packets (max_captured_packet_size + sizeof(fastnetmon_pcap_pkthdr_t)) + sizeof(fastnetmon_pcap_file_header_t). With `max_captured_packet_size = 1500` and sizeof(fastnetmon_pcap_pkthdr_t) = 16, each packet slot requires ~1516 bytes. The `buffer_size_in_packets` value is derived from the configuration parameter ban_details_records_count, which is parsed via `atoi()` without overflow validation. If an attacker or administrator sets `ban_details_records_count` to a value greater than approximately 2,832,542, the multiplication overflows a 32-bit unsigned integer. The overflow reduces the computed `memory_size_in_bytes` to a small number (e.g., modulo 2^32), causing the heap allocation to be far smaller than needed. Later, `write_packet()` calls copy packet data into this undersized buffer, writing past its bounds and corrupting heap metadata. This can lead to denial of service, arbitrary code execution, or complete system compromise depending on heap layout and subsequent memory operations.
dailycve form:
Platform: FastNetMon Community
Version: up to 1.2.9
Vulnerability: Integer overflow buffer
Severity: Critical
date: 05/26/2026
Prediction: 2026-06-10
What Undercode Say:
Analytics – Bash commands to detect risky config:
Check current ban_details_records_count value grep -i "ban_details_records_count" /etc/fastnetmon.conf Calculate overflow threshold (approx 2.83 million) echo $(( (232) / (1500+16) ))
Exploit:
Set `ban_details_records_count = 3000000` in config, restart FastNetMon. Observe heap corruption and crash via dmesg | grep -i "corrupted".
Protection from this CVE:
Upgrade to patched version (>1.2.9) or apply vendor patch. If unavailable, limit `ban_details_records_count` to ≤2,800,000 and validate input using `strtoul()` instead of atoi().
Impact:
Heap corruption leading to denial of service (crash) or remote code execution (RCE) via crafted packet bursts triggering the undersized buffer.
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Sources:
Reported By: nvd.nist.gov
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