CVE-2025-20311
CVE-2025-20311 is a high-severity vulnerability with a CVSS 3.x base score of 7.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-19.
Key facts
- Severity: High (CVSS 3.x base score 7.4)
- EPSS exploit prediction: 0% (9th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2025-31032
- Weakness: CWE-19
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2025-20311?
- 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.
- How severe is CVE-2025-20311?
- CVE-2025-20311 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
- Is CVE-2025-20311 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2025-20311?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2025-20311 have an EU (EUVD) identifier?
- Yes. CVE-2025-20311 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-31032.
- When was CVE-2025-20311 published?
- CVE-2025-20311 was published on 2025-09-24 and last updated on 2026-06-17.
References
Other CWE-19 vulnerabilities
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- CVE-2014-4488 — Critical (CVSS 10.0): IOHIDFamily in Apple iOS before 8.1.3, Apple OS X before 10.10.2, and Apple TV before 7.0.3 does not properly validate…
- CVE-2014-7247 — Critical (CVSS 10.0): Unspecified vulnerability in JustSystems Ichitaro 2008 through 2011; Ichitaro Government 6, 7, 2008, 2009, and 2010;…
- CVE-1999-0226 — Critical (CVSS 10.0): Windows NT TCP/IP processes fragmented IP packets improperly, causing a denial of service.