# CVE-2026-48686: FastNetMon Community Edition stack overflow in BGP NLRI decoder

Source: https://junglewise.ai/threats/cve-2026-48686-fastnetmon-community-edition-stack-overflow-in-bgp-nlri-decoder  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-26. Updated: 2026-05-26  
License: CC BY 4.0 with a link back

CVE-2026-48686 · Severity: info · CVSS 9.8 · Published 2026-05-26

FastNetMon is a high-performance DDoS sensor used by network administrators to monitor traffic and detect attacks. A critical vulnerability in its BGP protocol handling allows a remote attacker to execute malicious code on the system. By sending a specially crafted BGP message, an attacker can crash the service or gain full control over the monitoring server, potentially leading to a complete compromise of the network monitoring infrastructure.

## Quick answers

**Is CVE-2026-48686 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-48686 being exploited in the wild.

**How severe is CVE-2026-48686?** Informational severity, with a CVSS score of 9.8, published 26 May 2026.

**Which products and versions are affected?** FastNetMon FastNetMon Community Edition through 1.2.9.

**Is there a fix for CVE-2026-48686?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-48686 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-48686?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stack-based buffer overflow exists in the `decode_bgp_subnet_encoding_ipv4_raw()` function within `src/bgp_protocol.cpp`. The function reads a `prefix_bit_length` value directly from a BGP packet without validating that it is within the expected range for IPv4 (0-32). This value is used to calculate a copy length of up to 32 bytes, which is then passed to `memcpy()` to populate a 4-byte `uint32_t` stack variable. An attacker can overflow the stack by up to 28 bytes, overwriting the saved return address. Because the software is often compiled without stack canaries or Position Independent Executable (PIE) protections, this provides a reliable primitive for remote code execution. The vulnerability is reachable via any BGP peer session.

## Affected products

- FastNetMon FastNetMon Community Edition through 1.2.9

## Timeline

- 2026-05-23: disclosed: Vulnerability details published by Lorikeet Security
- 2026-05-26: advisory: CVE-2026-48686 published in NVD

## References

- [https://github.com/pavel-odintsov/fastnetmon](https://github.com/pavel-odintsov/fastnetmon)
- [https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.cpp](https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.cpp)
- [https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48686-bgp-nlri-stack-overflow](https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48686-bgp-nlri-stack-overflow)