CVE-2025-24356Network attack vector

Distributed denial of service via UDP amplification

Published Jan 27, 2025 · Updated Jan 28, 2025

Asymmetric resource consumption in fastd before 23 allows remote attackers to amplify spoofed UDP traffic for distributed denial of service. The fast-reconnect receive path treats a one-byte packet from an unknown address and port as peer movement, emits an approximately 150-byte handshake, and rate-limits unknown peers per port rather than per address. Only internet-reachable instances that allow connections from arbitrary IP addresses expose the amplification; clients with configured remote peers do not.

CVSS severity6.9
Medium
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Asymmetric resource consumption in fastd before 23 allows remote attackers to amplify spoofed UDP traffic for distributed denial of service. The fast-reconnect receive path treats a one-byte packet from an unknown address and port as peer movement, emits an approximately 150-byte handshake, and rate-limits unknown peers per port rather than per address. Only internet-reachable instances that allow connections from arbitrary IP addresses expose the amplification; clients with configured remote peers do not.

The record

CVE
CVE-2025-24356
Published
Jan 27, 2025
Updated
Jan 28, 2025
Vendor
Neocturne
Product
fastd
Classifications
CWE-405, T1498.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Jan 28, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 23

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Neocturne · fastdversion=< 23

Published CVSS scores

6.9GitHub Security AdvisoryCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-405Asymmetric Resource Consumption (Amplification)
T1498.002Network Denial of Service: Reflection Amplification

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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