Vulnerability in Cisco iOS Xe Software
CVE-2026-20004
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (6.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 6.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- Cisco iOS Xe Software — versions 16.9.1, 16.9.2, 16.9.1a
- Cisco iOS Xe — versions 16.10.1, 16.10.1a, 16.10.1b
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-20004?
- CVE-2026-20004 is a high-severity vulnerability in Cisco iOS Xe Software, classified under CWE-771. CVSS score: 7.4/10. Published 2026-03-25.
- How severe is CVE-2026-20004?
- High severity. CVSS v3 base score is 7.4 out of 10.