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iOSOperating system · Cisco

CVE-2024-20465

MEDIUM · 5.8 CVSS v3.1 Published 2024-09-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
67/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability in the access control list (ACL) programming of Cisco IOS Software running on Cisco Industrial Ethernet 4000, 4010, and 5000 Series Switches could allow an unauthenticated, remote attacker to bypass a configured ACL. This vulnerability is due to the incorrect handling of IPv4 ACLs on switched virtual interfaces when an administrator enables and disables Resilient Ethernet Protocol (REP). An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to bypass an ACL on the affected device.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

This vulnerability allows unauthenticated remote attackers to bypass configured IPv4 ACLs on switched virtual interfaces (SVIs) on affected Cisco Industrial Ethernet switches. The bug is triggered when an administrator enables and then disables Resilient Ethernet Protocol (REP), causing the ACL programming to incorrectly handle IPv4 ACLs on SVIs. A successful exploit lets traffic pass through the device without being filtered by the configured ACL.

MitigationApply the Cisco software update (when available) that addresses this vulnerability. In the interim, review ACL configurations on affected devices and monitor for unexpected traffic patterns.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
iOSOperating system
Affected:= 15.2\(8\)e2= 15.2\(8\)e3= 15.2\(8\)e4= 15.2\(8\)e5

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check the Cisco iOS version
    Use 'show version' command to display the running iOS version
    Affected if The version shown is 15.2(8)e2, 15.2(8)e3, 15.2(8)e4, or 15.2(8)e5
  2. Determine if REP was ever enabled
    Use 'show rep topology' or check the running configuration for 'rep segment' commands under the interfaces
    Affected if REP configuration exists in the running config or REP topology information is present
  3. Confirm REP was disabled after being enabled
    Review the configuration for absence of 'rep segment' commands while checking logs or configuration history for prior REP presence
    Affected if REP was previously configured but is now absent from the current configuration
  4. Identify IPv4 ACLs applied to SVIs
    Use 'show ip interface' and 'show running-config | include interface Vlan' along with 'show access-lists' to identify ACLs on SVI interfaces
    Affected if IPv4 access lists are configured and applied to switched virtual interfaces (SVIs)
  5. Verify ACL behavior on SVI traffic
    Use 'show access-lists' with traffic testing or compare ACL hit counts against actual traffic patterns to confirm ACLs are processing packets as expected
    Affected if IPv4 ACLs applied to SVIs show no hits or unexpected traffic passes when it should be denied based on ACL rules

A device is affected if it runs Cisco iOS version 15.2(8)e2-e5, had REP enabled and then disabled, and has IPv4 ACLs applied to SVIs - in which case ACL filtering may not be functioning correctly on SVI traffic.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Cisco software update (when available) that addresses this vulnerability. In the interim, review ACL configurations on affected devices and monitor for unexpected traffic patterns.

Fix this in iOS Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-20465 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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