CVE-2020-3255Network attack vector

Transit-traffic denial of service via packet flood

Published May 6, 2020 · Updated Nov 15, 2024

Denial of service in Cisco Firepower Threat Defense allows remote attackers to interrupt transit traffic with a packet flood. Its packet-processing path manages memory inefficiently when high-rate IPv4 or IPv6 traffic matches a block action, exhausting device memory. Exploitation requires a configured access-control block action; transit traffic stops and management becomes sluggish until the flood ends.

CVSS severity7.5
High
EPSS probability1.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco Firepower Threat Defense allows remote attackers to interrupt transit traffic with a packet flood. Its packet-processing path manages memory inefficiently when high-rate IPv4 or IPv6 traffic matches a block action, exhausting device memory. Exploitation requires a configured access-control block action; transit traffic stops and management becomes sluggish until the flood ends.

The record

CVE
CVE-2020-3255
Published
May 6, 2020
Updated
Nov 15, 2024
Vendor
ClamAV
Product
Cisco Firepower Threat Defense
Classifications
CWE-400, T1498.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 6, 2020CVE publishedPublication date reported by the CVE source.
  2. Nov 15, 2024Record 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=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Firepower Threat Defenseversion=n/a

Published CVSS scores

7.5Cisco Systems, Inc.CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:X/RL:X/RC:X
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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-400Uncontrolled Resource Consumption
T1498.001Direct Network Flood

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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