# CVE-2026-48691: FastNetMon Community Edition heap overflow in BGP AS_PATH encoder

Source: https://junglewise.ai/threats/cve-2026-48691-fastnetmon-community-edition-heap-overflow-in-bgp-as-path-encoder  
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-2026-48691 · Severity: info · CVSS 7.5 · Published 2026-05-26

FastNetMon Community Edition, a DDoS detection and traffic analysis tool, contains a vulnerability in how it handles network routing information. When the software processes or forwards routing updates with long path data, it incorrectly calculates the size of the memory needed to store that data. This error can allow a remote attacker to crash the service or potentially gain unauthorized control over the system by sending specially crafted network messages.

Technologies: [FastNetMon LTD FastNetMon Community Edition](https://junglewise.ai/threats/technologies/fastnetmon-community-edition). Vendors: [FastNetMon LTD](https://junglewise.ai/threats/vendors/fastnetmon-ltd).

## Quick answers

**Is CVE-2026-48691 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-48691 being exploited in the wild.

**How severe is CVE-2026-48691?** Informational severity, with a CVSS score of 7.5, published 26 May 2026.

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

**Is there a fix for CVE-2026-48691?** 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-2026-48691 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-48691?** Check whether you run FastNetMon LTD FastNetMon Community Edition at an affected version. 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

An integer overflow exists in the BGP AS_PATH attribute encoder within `src/bgp_protocol.hpp`. The function `IPv4UnicastAnnounce::get_attributes()` calculates the `attribute_length` for an AS_PATH but stores the result in a `uint8_t` variable. When an AS_PATH contains more than 63 ASNs, the length calculation (2 + ASNs * 4) exceeds 255 and silently truncates. This truncated value is used to allocate a heap buffer via `set_maximum_buffer_size()`, but the subsequent loop writes the full, untruncated list of 32-bit ASNs into the undersized buffer. An attacker can trigger this by injecting long AS_PATHS via BGP peers or through the unauthenticated gRPC API's `ExecuteBan` method, potentially leading to remote code execution. As of May 2026, no official patch has been released.

## Affected products

- FastNetMon LTD FastNetMon Community Edition through 1.2.9

## Timeline

- 2026-04-25: other: Vendor notified by Lorikeet Security
- 2026-05-23: advisory: Public disclosure by Lorikeet Security
- 2026-05-26: disclosed: CVE-2026-48691 published to 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.hpp](https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hpp)
- [https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflow](https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflow)

## Related threats

- [FastNetMon Community Edition configuration injection in Juniper plugin](https://junglewise.ai/threats/cve-2026-48694-fastnetmon-community-edition-configuration-injection-in-juniper)
- [FastNetMon Community Edition improper TLS certificate validation in telemetry](https://junglewise.ai/threats/cve-2026-48697-fastnetmon-community-edition-improper-tls-certificate-validation)
- [FastNetMon Community Edition heap overflow in packet capture buffer](https://junglewise.ai/threats/cve-2026-48690-fastnetmon-community-edition-heap-overflow-in-packet-capture)
- [FastNetMon Community Edition out-of-bounds read in NetFlow v9 parser](https://junglewise.ai/threats/cve-2026-48684-fastnetmon-community-edition-out-of-bounds-read-in-netflow-v9)
- [FastNetMon Community Edition out-of-bounds read in NetFlow v9 collector](https://junglewise.ai/threats/cve-2026-48683-fastnetmon-community-edition-out-of-bounds-read-in-netflow-v9)