ACL bypass via mutually exclusive interface programming
Published May 7, 2025 · Updated May 7, 2025
ACL programming in Cisco IOS on Catalyst 1000 and 2960-L switches allows remote attackers to bypass configured traffic restrictions. When an interface combines an IPv4 access-group with IP Source Guard, IOS programs only one ACL at a time; command order and later IP Source Guard changes determine which policy remains active. Exploitation requires the unsupported dual-ACL configuration and traffic through the affected interface, allowing access to resources that the inactive ACL was intended to protect.
Summary
What happened
ACL programming in Cisco IOS on Catalyst 1000 and 2960-L switches allows remote attackers to bypass configured traffic restrictions. When an interface combines an IPv4 access-group with IP Source Guard, IOS programs only one ACL at a time; command order and later IP Source Guard changes determine which policy remains active. Exploitation requires the unsupported dual-ACL configuration and traffic through the affected interface, allowing access to resources that the inactive ACL was intended to protect.
The record
- CVE
- CVE-2025-20137
- Published
- May 7, 2025
- Updated
- May 7, 2025
- Vendor
- ClamAV
- Product
- Cisco IOS
- Classifications
- CWE-284, T1599
- Attack vector
- adjacent
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 7, 2025CVE publishedPublication date reported by the CVE source.
- May 7, 2025Record 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.
- Affected versionversion=15.2(5a)E
- Affected versionversion=15.2(5b)E
- Affected versionversion=15.2(5c)E
- Affected versionversion=15.2(6)E
- Affected versionversion=15.2(6)E0c
- Affected versionversion=15.2(6)E1
- Affected versionversion=15.2(6)E2
- Affected versionversion=15.2(6)E2b
- Affected versionversion=15.2(6)E3
- Affected versionversion=15.2(7a)E0b
- Affected versionversion=15.2(7b)E0b
- Affected versionversion=15.2(7)E
- Affected versionversion=15.2(7)E0a
- Affected versionversion=15.2(7)E0s
- Affected versionversion=15.2(7)E1
- Affected versionversion=15.2(7)E10
- Affected versionversion=15.2(7)E11
- Affected versionversion=15.2(7)E12
- Affected versionversion=15.2(7)E1a
- Affected versionversion=15.2(7)E2
- Affected versionversion=15.2(7)E3
- Affected versionversion=15.2(7)E3k
- Affected versionversion=15.2(7)E4
- Affected versionversion=15.2(7)E5
- Affected versionversion=15.2(7)E6
- Affected versionversion=15.2(7)E7
- Affected versionversion=15.2(7)E8
- Affected versionversion=15.2(7)E9
- Affected versionversion=15.2(8)E
- Affected versionversion=15.2(8)E1
- Affected versionversion=15.2(8)E2
- Affected versionversion=15.2(8)E3
- Affected versionversion=15.2(8)E4
- Affected versionversion=15.2(8)E5
- Affected versionversion=15.2(8)E6
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
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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