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CVE-2026-48691

9.8 · CRITICAL

FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder.

Published May 26, 2026CWE-190EPSS 0.57%

Overview

CVE-2026-48691 is a critical-severity vulnerability. It was published on May 26, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/pavel-odintsov/fastnetmonGitHubgithub.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.hppReflorikeetsecurity.com/blog/fastnetmon-cve-2026-48691-bgp-as-path-overflow

How CyberStrike helps

Frequently asked questions

What is CVE-2026-48691?

CVE-2026-48691 is a critical-severity vulnerability. It was published on May 26, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-48691?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-48691?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-48691?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-48691 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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