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How the CVE Works
CVE-2025-20137 exploits a misconfiguration in Cisco IOS Software running on Catalyst 1000 and 2960L Switches. When an IPv4 ACL and a dynamic IP Source Guard ACL are applied on the same interface (an unsupported configuration), the switch fails to enforce proper access controls. An attacker can send crafted traffic through the device, bypassing intended restrictions. Cisco acknowledges this as an unsupported setup but has not implemented safeguards to prevent it, leaving devices vulnerable to ACL bypass.
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Platform: Cisco Catalyst Switches
Version: IOS (Catalyst 1000/2960L)
Vulnerability: ACL Bypass
Severity: Critical
Date: 08/05/2025
Prediction: Patch expected by Q4 2025
What Undercode Say
Analytics:
show running-config | include ip access-group show ip source guard binding debug ip packet detail
Exploit:
- Crafted IPv4 traffic sent to vulnerable interface.
- Bypasses ACL checks due to conflicting configurations.
Protection from this CVE
- Remove conflicting ACL configurations.
- Apply Cisco-recommended interface-level ACLs only.
Impact:
- Unauthorized network access.
- Potential lateral movement within the network.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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