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Out-of-bounds ReadWeakness · CWE-125

CVE-2026-48682

MEDIUM · 5.9 CVSS v3.1 Published 2026-06-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges 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 out-of-bounds read in the IPv4 packet parser. In src/simple_packet_parser_ng.cpp, after validating that the packet contains at least sizeof(ipv4_header_t) bytes (20 bytes), the code advances the local_pointer by '4 * ipv4_header->get_ihl()' (line 164) without validating that (a) IHL >= 5 (the minimum valid value per RFC 791), or (b) 4 * IHL bytes are actually available in the packet. The IHL field is 4 bits, allowing values 0-15, so the advance can be 0-60 bytes. An IHL value of 15 with only 20 bytes validated causes a 40-byte over-read. An IHL of 0-4 causes the pointer to not advance past the IP header, resulting in the TCP/UDP header being parsed from IP header data (type confusion). This vulnerability is reachable via any packet capture interface.

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 out-of-bounds read vulnerability in the IPv4 packet parser (src/simple_packet_parser_ng.cpp, line 164). The code validates packets contain at least 20 bytes but advances a pointer by '4 * ipv4_header->get_ihl()' without validating that IHL >= 5 (RFC 791 minimum) or that sufficient bytes exist. Malformed IHL values (0-4 or 15) enable 40-byte over-reads or type confusion by parsing TCP/UDP headers from IP header data.

MitigationFix requires adding bounds validation: (1) verify IHL >= 5 before use, and (2) ensure 4*IHL bytes are available in the packet buffer before advancing the pointer. Deploy updated version after testing with malformed packet sequences.

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

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
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/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 Community Edition version
    Check the installed version by running 'fastnetmon --version' or inspecting the package manager output (e.g., 'dpkg -l | grep fastnetmon' or 'rpm -qi fastnetmon'). Also check for version file at /opt/fastnetmon/version or within the source directory if self-compiled.
    Affected if The installed version is 1.2.9 or earlier (any version through 1.2.9 is affected).
  2. Confirm IPv4 packet processing is active
    Examine FastNetMon configuration files (typically /etc/fastnetmon.conf or /opt/fastnetmon/fastnetmon.conf) for enable_parsing or similar IPv4-related settings. Review the startup logs or running process parameters to confirm packet parsing is enabled.
    Affected if IPv4 packet parsing is enabled (this is the default and expected configuration for FastNetMon as a network monitoring tool).
  3. Verify the vulnerable parser component is in use
    Check if the binary links against or includes simple_packet_parser_ng.cpp. On Linux, use 'ldd <fastnetmon_binary>' or inspect the compiled binary. If built from source, verify src/simple_packet_parser_ng.cpp exists in the build directory.
    Affected if The simple_packet_parser_ng.cpp component is present and used for IPv4 packet parsing (default behavior for community edition).

A user is affected if they run FastNetMon Community Edition version 1.2.9 or earlier with IPv4 packet parsing enabled, as the vulnerable code path in simple_packet_parser_ng.cpp will process packets without proper IHL validation.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Fix requires adding bounds validation: (1) verify IHL >= 5 before use, and (2) ensure 4*IHL bytes are available in the packet buffer before advancing the pointer. Deploy updated version after testing with malformed packet sequences.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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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-2026-48682 in production — separate from our analysis above.

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What this is

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