CVE-2025-20316Network attack vector

Unauthenticated ACL bypass via unlearned-MAC flooding

Published Sep 24, 2025 · Updated Sep 24, 2025

Improper access control in Cisco IOS XE Software on Catalyst 9500X and 9600X switches allows remote attackers to bypass an egress ACL. Traffic from an unlearned MAC address is flooded from an SVI with an egress ACL after the VLAN MAC table is flushed or becomes full. No authentication is required, but an affected switch must run a vulnerable release and have an egress ACL on an SVI; bypassed traffic can cross the intended policy boundary.

CVSS severity5.3
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Cisco IOS XE Software on Catalyst 9500X and 9600X switches allows remote attackers to bypass an egress ACL. Traffic from an unlearned MAC address is flooded from an SVI with an egress ACL after the VLAN MAC table is flushed or becomes full. No authentication is required, but an affected switch must run a vulnerable release and have an egress ACL on an SVI; bypassed traffic can cross the intended policy boundary.

The record

CVE
CVE-2025-20316
Published
Sep 24, 2025
Updated
Sep 24, 2025
Vendor
ClamAV
Product
Cisco IOS XE Software
Classifications
CWE-284, T1562.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 24, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=17.10.1
  2. Affected versionversion=17.10.1b
  3. Affected versionversion=17.11.1
  4. Affected versionversion=17.12.1
  5. Affected versionversion=17.12.2
  6. Affected versionversion=17.12.3
  7. Affected versionversion=17.12.4
  8. Affected versionversion=17.12.5
  9. Affected versionversion=17.13.1
  10. Affected versionversion=17.14.1
  11. Affected versionversion=17.15.1
  12. Affected versionversion=17.15.2
  13. Affected versionversion=17.15.2b
  14. Affected versionversion=17.15.3
  15. Affected versionversion=17.16.1
  16. Affected versionversion=17.17.1
  17. Affected versionversion=17.7.1
  18. Affected versionversion=17.8.1
  19. Affected versionversion=17.9.1
  20. Affected versionversion=17.9.2
  21. Affected versionversion=17.9.3
  22. Affected versionversion=17.9.4
  23. Affected versionversion=17.9.4a
  24. Affected versionversion=17.9.5
  25. Affected versionversion=17.9.6
  26. Affected versionversion=17.9.6a
  27. Affected versionversion=17.9.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco IOS XE Softwareversion=17.10.1; version=17.10.1b; version=17.11.1; version=17.12.1; version=17.12.2; version=17.12.3; version=17.12.4; version=17.12.5; version=17.13.1; version=17.14.1; version=17.15.1; version=17.15.2; version=17.15.2b; version=17.15.3; version=17.16.1; version=17.17.1; version=17.7.1; version=17.8.1; version=17.9.1; version=17.9.2; version=17.9.3; version=17.9.4; version=17.9.4a; version=17.9.5; version=17.9.6; version=17.9.6a; version=17.9.7

Published CVSS scores

5.3CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:X/RL:X/RC:X

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-284Improper Access Control
T1562.004Impair Defenses: Disable or Modify System Firewall

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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