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Vulnerabilities

Vulnerability · 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.

Published Mar 25, 2026 · catalog updated Sep 28, 2026 · ios xe

Check if you run it

No confirmed exploitation is on record for CVE-2026-20004. EPSS is 0.18%. Act only if a listed version of ios xe is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.4
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.18%
Remediation
Advisory link
Affected products
cpe cisco/ios xe

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe cisco/ios xe16.9.1
  • cpe cisco/ios xe16.9.1a
  • cpe cisco/ios xe16.9.1b
  • cpe cisco/ios xe16.9.1s
  • cpe cisco/ios xe16.9.2
  • cpe cisco/ios xe16.9.3
  • cpe cisco/ios xe16.9.3a
  • cpe cisco/ios xe16.9.4

How to fix CVE-2026-20004

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-20004. EPSS is 0.18%. Act only if a listed version of ios xe is installed.

Which versions are affected?

Compare what you have installed with cisco/ios xe 16.9.1; cisco/ios xe 16.9.1a; cisco/ios xe 16.9.1b; cisco/ios xe 16.9.1s. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-771. EPSS 0.18%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 25, 2026 · NIST NVD

    Detected

    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 i

  2. Sep 28, 2026 · NIST NVD

    Updated

    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 i

Sources

  • CVE.orgVulnerability recordCVE-2026-20004

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-20004

    30-day exploitation probability 0.2%

    first.org
  • NIST NVDVulnerability recordCVE-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 co

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.