CVE-2020-3231

Pre-auth broadcast forwarding via 802.1X mishandling

Published Jun 3, 2020 · Updated Nov 15, 2024

Authentication bypass in Cisco IOS on Catalyst 2960-L and CDB-8P switches allows attackers to forward broadcast traffic before authentication. The 802.1X-enabled port mishandles broadcast frames received before the attached endpoint authenticates, forwarding traffic that access control should block. Exploitation requires adjacent access to an affected switch port with 802.1X port-based authentication configured and permits only pre-authentication broadcast traffic exchange.

CVSS severity4.7
Medium
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Cisco IOS on Catalyst 2960-L and CDB-8P switches allows attackers to forward broadcast traffic before authentication. The 802.1X-enabled port mishandles broadcast frames received before the attached endpoint authenticates, forwarding traffic that access control should block. Exploitation requires adjacent access to an affected switch port with 802.1X port-based authentication configured and permits only pre-authentication broadcast traffic exchange.

The record

CVE
CVE-2020-3231
Published
Jun 3, 2020
Updated
Nov 15, 2024
Vendor
ClamAV
Product
Cisco IOS
Classifications
CWE-284, CWE-863
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 3, 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?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco IOSversion=n/a

Published CVSS scores

4.7NIST National Vulnerability DatabaseCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
4.7Cisco Systems, Inc.CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N/E:X/RL:X/RC:X
2.9NIST National Vulnerability DatabaseAV:A/AC:M/Au:N/C:P/I:N/A:N

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.

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No observations available

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

Weakness, pattern, technique

CWE-284Improper Access Control
CWE-863Incorrect Authorization

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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