dbcve.org
FastnetmonApplication · Pavel Odintsov

CVE-2026-48690

HIGH · 7.1 CVSS v3.1 Published 2026-05-26
Fix available
A fix is available. Upgrade to after 1.2.9 or later.
See remediation →
73/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
FastNetMon Community Edition through 1.2.9 contains an integer overflow vulnerability in the packet capture buffer allocation. In src/packet_storage.hpp, the allocate_buffer() function computes memory_size_in_bytes as 'buffer_size_in_packets * (max_captured_packet_size + sizeof(fastnetmon_pcap_pkthdr_t)) + sizeof(fastnetmon_pcap_file_header_t)' using unsigned int (32-bit) arithmetic. With max_captured_packet_size=1500 and sizeof(fastnetmon_pcap_pkthdr_t)=16, each packet requires approximately 1516 bytes. If buffer_size_in_packets exceeds approximately 2,832,542, the multiplication overflows, resulting in a much smaller allocation than expected. Subsequent write_packet() calls then write past the allocated buffer, causing heap corruption. The buffer_size_in_packets value is derived from the ban_details_records_count configuration parameter, which is parsed using atoi() with no overflow checking.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

FastNetMon Community Edition through 1.2.9 has an integer overflow in src/packet_storage.hpp's allocate_buffer() function. The buffer size calculation uses 32-bit unsigned integer arithmetic multiplying buffer_size_in_packets by ~1516 bytes per packet. When buffer_size_in_packets (derived from ban_details_records_count config via atoi()) exceeds ~2,832,542, the multiplication overflows, allocating a much smaller buffer than required. Subsequent write_packet() calls then overflow the undersized buffer, causing heap corruption.

MitigationAdd bounds checking on the ban_details_records_count configuration value before use, and refactor the buffer size calculation to use 64-bit integer arithmetic (e.g., uint64_t) to prevent overflow.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FastnetmonApplication
Affected:<= 1.2.9

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify FastNetMon version
    Run 'fastnetmon --version' or check the installed package version via your package manager (dpkg -l | grep fastnetmon or rpm -qi fastnetmon)
    Affected if Version is 1.2.9 or earlier
  2. Locate FastNetMon configuration file
    Common locations: /etc/fastnetmon.conf, /etc/fastnetmon/fastnetmon.conf, or check /opt/fastnetmon/config/. If installed from source, check the directory where you deployed it.
    Affected if Configuration file cannot be located or does not exist
  3. Find ban_details_records_count setting
    Open the configuration file and search for 'ban_details_records_count' parameter. This is parsed via atoi() without overflow validation.
    Affected if Parameter is present in configuration
  4. Check if ban_details_records_count exceeds overflow threshold
    Read the numeric value assigned to ban_details_records_count. The vulnerable threshold is approximately 2,832,542 packets.
    Affected if ban_details_records_count value is greater than 2832542
  5. Verify if using 32-bit compiled binary
    Run 'file /usr/bin/fastnetmon' or 'file /usr/local/bin/fastnetmon' (path depends on installation). Check if it is compiled as 32-bit (i386) versus 64-bit (x86-64). The vulnerability exists in 32-bit arithmetic paths.
    Affected if Binary is compiled and uses 32-bit unsigned int for buffer_size_in_bytes calculation

If FastNetMon version is 1.2.9 or earlier AND ban_details_records_count is configured with a value exceeding approximately 2,832,542, the environment is affected by the integer overflow vulnerability leading to potential heap corruption.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 1.2.9
Interim mitigation

Add bounds checking on the ban_details_records_count configuration value before use, and refactor the buffer size calculation to use 64-bit integer arithmetic (e.g., uint64_t) to prevent overflow.

Recommended fix Moderate confidence

Fastnetmon 1.3.0 or later

  1. 1. Identify the current Fastnetmon version by running 'fastnetmon --version' or checking the package manager
  2. 2. Locate the ban_details_records_count parameter in fastnetmon.conf (or equivalent configuration file)
  3. 3. Verify the current value of ban_details_records_count - ensure it is set below 2,832,542 to prevent the integer overflow
  4. 4. Upgrade Fastnetmon to version 1.3.0 or later by following the official installation guide for your package manager (apt/yum) or compiling from source
  5. 5. After upgrade, verify the version with 'fastnetmon --version' to confirm the fix is applied
  6. 6. Restart the Fastnetmon service to load the new version
  7. 7. Validate that packet capture continues正常工作 (working normally) and no heap corruption errors appear in logs

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fastnetmon Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-48690 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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