CVE-2026-48686

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Summary

CVECVE-2026-48686
StatePUBLISHED
Assignermitre
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-26 16:16:26 UTC
Updated2026-05-27 14:23:43 UTC
DescriptionFastNetMon 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-120 | CWE-787 | n/a | CWE-787 CWE-787 Out-of-bounds Write | CWE-120 CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1ADPDECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Pavel-odintsov Fastnetmon All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Na N/a affected n/a Not specified

References

ReferenceSourceLinkTags
github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.cpp [email protected] github.com Product
lorikeetsecurity.com/blog/fastnetmon-cve-2026-48686-bgp-nlri-stack-overflow [email protected] lorikeetsecurity.com Third Party Advisory
github.com/pavel-odintsov/fastnetmon [email protected] github.com Product
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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