Medium

ACL Bypass in Cisco IOS XE Catalyst 9500X and 9600X Series Switches

IdentifiersCVE-2025-20316CWE-284· Improper Access Control

CVE-2025-20316 is an access control vulnerability in the ACL programming behavior of Cisco IOS XE Software affecting Cisco Catalyst 9500X and 9600X Series Switches. According to the provided content, the issue occurs when traffic sourced from an unlearned MAC address is flooded on a switch virtual interface (SVI) that has an egress ACL applied. An attacker can trigger the condition by causing the VLAN to flush its MAC address table; the same condition may also arise when the MAC address table is full. Under these circumstances, traffic may be forwarded in a way that bypasses the configured egress ACL, resulting in an ACL enforcement failure on the affected device.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

A successful exploit allows an unauthenticated remote attacker to bypass a configured egress ACL on an affected Cisco IOS XE device. This can undermine intended network segmentation and traffic-filtering policy enforcement, permitting traffic that should have been blocked by the ACL to traverse the device.

Mitigation

If you can’t patch tonight, do this now.

No specific workaround or mitigation beyond vendor-directed software updates is provided in the supplied content. Operationally, reducing conditions that cause MAC table flushes or MAC table exhaustion may reduce exposure, but the authoritative mitigation information currently available in the provided content is to follow Cisco’s advisory and upgrade guidance.

Remediation

Patch, then assume compromise.

Cisco recommends updating affected products in accordance with the vendor’s advisory and device/version-specific guidance. Apply the fixed Cisco IOS XE software release for affected Catalyst 9500X and 9600X Series Switches as identified by Cisco.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

5 SOURCESView more in app

kyberturvallisuuskeskus alertsNews

Sep 26, 2025

Haavoittuvuuksia Cisco IOS ja IOS XE -laitteissa | Traficom

An access control bypass vulnerability in certain Cisco IOS XE devices.

kyberturvallisuuskeskus alertsNews

Sep 26, 2025

Haavoittuvuuksia Cisco IOS ja IOS XE -laitteissa | Traficom

An access control bypass vulnerability affecting certain Cisco IOS XE devices.

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

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