Is CVE-2026-20004 being actively exploited?

CVE-2026-20004 is not currently listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

What is the CVSS score for CVE-2026-20004?

CVE-2026-20004 has a CVSS 3.1 base score of 7.4 (HIGH).

CVE-2026-20004

HIGH · CVSS 7.4EPSS 0.2%EU EUVD

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.

Key facts

CVSS score: 7.4 (v3.1)
Severity: HIGH
CVSS vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Weakness (CWE): CWE-771
EPSS score: 0.2% (7th percentile)
In CISA KEV: No
In EU EUVD: Yes (EUVD-2026-15426)
Published: March 25, 2026
NVD last modified: September 28, 2026
Status: Analyzed

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2026-15426 in the EU Vulnerability Database. Last updated in EUVD on March 26, 2026.

View on the EU Vulnerability Database

Affected products

cisco / ios xe
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and 130 more…

Certified products that may be affected

11 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

Cisco Embedded Services 9300 and 3300 Series Switches (ESS9300 & ESS3300) running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11662-2026 - active
Cisco Catalyst 8000V Edge (C8000V) running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria Certificate Number: 2025/161 - active
Cisco 1000 Series Integrated Services Routers (C1100), Cisco Catalyst IR1800 Rugged Series Routers (IR1800), Cisco Catalyst IR8300 Rugged Series Routers (IR8300) running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11643-2025 - active
Cisco Catalyst Industrial Ethernet 9300 Rugged Series Switches running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11603-2025 - active
Cisco Aggregation Services Router 1000 Series (ASR1K), Cisco Catalyst 8200, 8300, 8500 Series Edge Routers (Cat8K) running IOS-XE version 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11642-2025 - active

See all 11 in the Security Certifications Explorer.

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-tls-dos-TVgLDEZL(Vendor Advisory)

Last updated September 30, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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