CVE-2026-20004

CVE-2026-20004 is a high-severity vulnerability in Cisco Ios Xe 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-771.

Key facts

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-20004?
CVE-2026-20004 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-2026-20004 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (7th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-20004?
CVE-2026-20004 primarily affects Cisco Ios Xe. In total, 180 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-20004?
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-2026-20004 have an EU (EUVD) identifier?
Yes. CVE-2026-20004 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-15426.
When was CVE-2026-20004 published?
CVE-2026-20004 was published on 2026-03-25 and last updated on 2026-09-28.

References

Affected products (180)

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