CVE-2026-48686

FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI (Network Layer Reachability Information) decoder. The function decode_bgp_subnet_encoding_ipv4_raw() in src/bgp_protocol.cpp reads prefix_bit_length directly from the BGP packet (line 99) without validating it is <= 32 for IPv4 prefixes. This value is passed to how_much_bytes_we_need_for_storing_certain_subnet_mask() which computes ceil(prefix_bit_length / 8), returning up to 32 bytes for a prefix_bit_length of 255. The result is used as the length argument to memcpy() (line 106), which copies into a 4-byte uint32_t stack variable (prefix_ipv4). This causes a stack buffer overflow of up to 28 bytes, which can be exploited for arbitrary code execution. Additionally, the unvalidated prefix_bit_length is passed to convert_cidr_to_binary_netmask_local_function_copy() (line 111), where a shift of (32 - cidr) with cidr > 32 causes undefined behavior.

CVSS v3 9.8 CRITICAL

9.8^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/pavel-odintsov/fastnetmon	Product
https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.cpp	Product
https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48686-bgp-nlri-stack-overflow	Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:pavel-odintsov:fastnetmon:*:*:*:*:community:*:*:*

History

No history.

Information

Published : 2026-05-26 16:16

Updated : 2026-07-24 11:10

NVD link : CVE-2026-48686

Mitre link : CVE-2026-48686

CVE.ORG link : CVE-2026-48686

JSON object : View

Products Affected

pavel-odintsov

fastnetmon

CWE

CWE-120

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

CWE-787

Out-of-bounds Write

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