CVE-2025-20311: Cisco IOS XE Software · Data Handling
Affects Cisco IOS XE SoftwareSource CVE Database V5
Not known to be exploited · CVSS 7.4 High.
Data as of 25 Oct 2026, 19:02 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 24 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Cisco Cisco IOS XE Software | Affected
| Fixed in– |
AI-suggested
To mitigate CVE-2025-20311 effectively, European organizations should take the following specific actions beyond generic patching advice: 1) Immediate deployment of Cisco-released patches or software updates that address this vulnerability across all affected Catalyst 9000 switches. Organizations should prioritize patching in network segments that handle critical or sensitive traffic. 2) Implement strict network segmentation and access controls to limit adjacency exposure. This includes enforcing VLAN segmentation, private VLANs, and port isolation to reduce the risk that an attacker can send crafted frames to vulnerable ports. 3) Deploy and configure network intrusion detection/prevention systems (IDS/IPS) capable of detecting anomalous or malformed Ethernet frames that could indicate exploitation attempts. 4) Monitor switch port status and traffic patterns for signs of egress port blocking or unusual frame drops, enabling rapid detection and response to exploitation attempts. 5) Harden internal network security by enforcing strong endpoint security, network access control (NAC), and limiting the ability of unauthorized devices to connect to critical network segments. 6) Conduct regular security audits and penetration tests focusing on internal network threats and the resilience of network infrastructure to crafted frame attacks. 7) Maintain an incident response plan that includes procedures for isolating affected network segments and restoring normal switch operation in case of exploitation. These targeted mitigations, combined with patch management, will reduce the risk and impact of this vulnerability in operational environments.
Description
A vulnerability in the handling of certain Ethernet frames in Cisco IOS XE Software for Catalyst 9000 Series Switches could allow an unauthenticated, adjacent attacker to cause an egress port to become blocked and drop all outbound traffic. This vulnerability is due to improper handling of crafted Ethernet frames. An attacker could exploit this vulnerability by sending crafted Ethernet frames through an affected switch. A successful exploit could allow the attacker to cause the egress port to which the crafted frame is forwarded to start dropping all frames, resulting in a denial of service (DoS) condition.