CVE-2026-20004 Denial of service in Cisco IOS XE Software
An adjacent attacker can exhaust memory via TLS connection setup, causing a device reload and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20004?
CVE-2026-20004 is a high-severity denial of service vulnerability in Cisco Ios Xe, published on 25 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A vulnerability in the TLS library of Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to exhaust the available memory of an affected device. This vulnerability is due to improper management of memory resources during TLS connection setup. An attacker could exploit this vulnerability by repeatedly triggering the conditions that cause the memory increase. This could be done in a variety of ways, such as by repeatedly attempting Extensible Authentication Protocol (EAP) authentication when local EAP is enabled on an affected device or by using a machine-in-the-middle attack and resetting TLS connections between the affected device and other devices. A successful exploit could allow the attacker to exhaust the available memory on an affected device, resulting in an unexpected reload and a denial of service (DoS) condition.
Weakness: CWE-771
Which versions are affected by CVE-2026-20004?
It affects 1 product.
Products include Cisco Ios Xe.
How do I fix CVE-2026-20004?
No fix has been published for CVE-2026-20004 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-20004 being exploited?
There is no known exploitation of CVE-2026-20004 in the wild and no public exploit code.
Other vulnerabilities in Cisco Ios Xe
- CVE-2023-20198 Cisco IOS XE Web UI Privilege Escalation
- CVE-2018-0151 Cisco IOS Software and Cisco IOS XE Software Quality of Service Remote Code Execution
- CVE-2023-20273 Cisco IOS XE Web UI Command Injection
- CVE-2025-20188 Hardcoded credentials in Cisco IOS XE Software
- CVE-2021-34770 Cisco IOS XE Software for Catalyst 9000 Family Wireless Controllers CAPWAP Remote Code Execution Vulnerability
Sources
Also known as GHSA-xp4f-63f5-wmm9.