--- id: CVE-2026-20271 title: >- As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XE Software engineering team has conducted a comprehensive internal security review summary: >- As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XE Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that … severity: high cvss: 8.6 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H' cwe: - CWE-691 vendor: cisco product: ios_xe affected: - ios_xe = 16.6.2 - ios_xe = 16.6.3 - ios_xe = 16.6.4 - ios_xe = 16.6.4a - ios_xe = 16.6.4s - ios_xe = 16.6.5 - ios_xe = 16.6.5a - ios_xe = 16.6.5b - ios_xe = 16.6.6 - ios_xe = 16.6.7 - ios_xe = 16.6.7a - ios_xe = 16.6.8 - ios_xe = 16.6.9 - ios_xe = 16.6.10 - ios_xe = 16.7.1 - ios_xe = 16.7.1a - ios_xe = 16.7.1b - ios_xe = 16.7.2 - ios_xe = 16.7.3 - ios_xe = 16.7.4 - ios_xe = 16.8.1 - ios_xe = 16.8.1a - ios_xe = 16.8.1b - ios_xe = 16.8.1c - ios_xe = 16.8.1d - ios_xe = 16.8.1e - ios_xe = 16.8.1s - ios_xe = 16.8.2 - ios_xe = 16.8.3 - ios_xe = 16.9.1 - ios_xe = 16.9.1a - ios_xe = 16.9.1b - ios_xe = 16.9.1c - ios_xe = 16.9.1d - ios_xe = 16.9.1s - ios_xe = 16.9.2 - ios_xe = 16.9.2a - ios_xe = 16.9.2s - ios_xe = 16.9.3 - ios_xe = 16.9.3a - ios_xe = 16.9.3h - ios_xe = 16.9.3s - ios_xe = 16.9.4 - ios_xe = 16.9.4c - ios_xe = 16.9.5 - ios_xe = 16.9.5f - ios_xe = 16.9.6 - ios_xe = 16.9.7 - ios_xe = 16.9.8 - ios_xe = 16.9.8a - ios_xe = 16.9.8b - ios_xe = 16.10.1 - ios_xe = 16.10.1a - ios_xe = 16.10.1b - ios_xe = 16.10.1c - ios_xe = 16.10.1d - ios_xe = 16.10.1e - ios_xe = 16.10.1f - ios_xe = 16.10.1g - ios_xe = 16.10.1s - ios_xe = 16.10.2 - ios_xe = 16.10.3 - ios_xe = 16.11.1 - ios_xe = 16.11.1a - ios_xe = 16.11.1b - ios_xe = 16.11.1c - ios_xe = 16.11.1s - ios_xe = 16.11.2 - ios_xe = 16.12.1 - ios_xe = 16.12.1a - ios_xe = 16.12.1c - ios_xe = 16.12.1s - ios_xe = 16.12.1t - ios_xe = 16.12.1w - ios_xe = 16.12.1x - ios_xe = 16.12.1y - ios_xe = 16.12.1z - ios_xe = 16.12.1z1 - ios_xe = 16.12.1z2 - ios_xe = 16.12.2 - ios_xe = 16.12.2a - ios_xe = 16.12.2s - ios_xe = 16.12.2t - ios_xe = 16.12.3 - ios_xe = 16.12.3a - ios_xe = 16.12.3s - ios_xe = 16.12.4 - ios_xe = 16.12.4a - ios_xe = 16.12.5 - ios_xe = 16.12.5a - ios_xe = 16.12.5b - ios_xe = 16.12.6 - ios_xe = 16.12.6a - ios_xe = 16.12.7 - ios_xe = 16.12.8 - ios_xe = 16.12.9 - ios_xe = 16.12.10 - ios_xe = 16.12.10a - ios_xe = 16.12.11 - ios_xe = 16.12.12 published: '2026-08-05' updated: '2026-08-14' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-20271' references: - url: >- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxe-V8NMuMZJ label: psirt@cisco.com - url: >- https://www.cve.org/Media/News/item/blog/2026/06/16/Preserving-Vulnerability-Level-Identification label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://software.cisco.com' tags: - nvd - csaf - vendor-advisory - cisco epss: 0.00467 epssPercentile: 0.3774 ingestedAt: '2026-08-15T17:27:27.967Z' --- ## Overview As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XE Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20271 are related to insufficient control flow management issues that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-691.   ## Affected - `ios_xe = 16.6.2` - `ios_xe = 16.6.3` - `ios_xe = 16.6.4` - `ios_xe = 16.6.4a` - `ios_xe = 16.6.4s` - `ios_xe = 16.6.5` - `ios_xe = 16.6.5a` - `ios_xe = 16.6.5b` - `ios_xe = 16.6.6` - `ios_xe = 16.6.7` - `ios_xe = 16.6.7a` - `ios_xe = 16.6.8` - `ios_xe = 16.6.9` - `ios_xe = 16.6.10` - `ios_xe = 16.7.1` - `ios_xe = 16.7.1a` - `ios_xe = 16.7.1b` - `ios_xe = 16.7.2` - `ios_xe = 16.7.3` - `ios_xe = 16.7.4` - `ios_xe = 16.8.1` - `ios_xe = 16.8.1a` - `ios_xe = 16.8.1b` - `ios_xe = 16.8.1c` - `ios_xe = 16.8.1d` - `ios_xe = 16.8.1e` - `ios_xe = 16.8.1s` - `ios_xe = 16.8.2` - `ios_xe = 16.8.3` - `ios_xe = 16.9.1` - `ios_xe = 16.9.1a` - `ios_xe = 16.9.1b` - `ios_xe = 16.9.1c` - `ios_xe = 16.9.1d` - `ios_xe = 16.9.1s` - `ios_xe = 16.9.2` - `ios_xe = 16.9.2a` - `ios_xe = 16.9.2s` - `ios_xe = 16.9.3` - `ios_xe = 16.9.3a` - `ios_xe = 16.9.3h` - `ios_xe = 16.9.3s` - `ios_xe = 16.9.4` - `ios_xe = 16.9.4c` - `ios_xe = 16.9.5` - `ios_xe = 16.9.5f` - `ios_xe = 16.9.6` - `ios_xe = 16.9.7` - `ios_xe = 16.9.8` - `ios_xe = 16.9.8a` - `ios_xe = 16.9.8b` - `ios_xe = 16.10.1` - `ios_xe = 16.10.1a` - `ios_xe = 16.10.1b` - `ios_xe = 16.10.1c` - `ios_xe = 16.10.1d` - `ios_xe = 16.10.1e` - `ios_xe = 16.10.1f` - `ios_xe = 16.10.1g` - `ios_xe = 16.10.1s` - `ios_xe = 16.10.2` - `ios_xe = 16.10.3` - `ios_xe = 16.11.1` - `ios_xe = 16.11.1a` - `ios_xe = 16.11.1b` - `ios_xe = 16.11.1c` - `ios_xe = 16.11.1s` - `ios_xe = 16.11.2` - `ios_xe = 16.12.1` - `ios_xe = 16.12.1a` - `ios_xe = 16.12.1c` - `ios_xe = 16.12.1s` - `ios_xe = 16.12.1t` - `ios_xe = 16.12.1w` - `ios_xe = 16.12.1x` - `ios_xe = 16.12.1y` - `ios_xe = 16.12.1z` - `ios_xe = 16.12.1z1` - `ios_xe = 16.12.1z2` - `ios_xe = 16.12.2` - `ios_xe = 16.12.2a` - `ios_xe = 16.12.2s` - `ios_xe = 16.12.2t` - `ios_xe = 16.12.3` - `ios_xe = 16.12.3a` - `ios_xe = 16.12.3s` - `ios_xe = 16.12.4` - `ios_xe = 16.12.4a` - `ios_xe = 16.12.5` - `ios_xe = 16.12.5a` - `ios_xe = 16.12.5b` - `ios_xe = 16.12.6` - `ios_xe = 16.12.6a` - `ios_xe = 16.12.7` - `ios_xe = 16.12.8` - `ios_xe = 16.12.9` - `ios_xe = 16.12.10` - `ios_xe = 16.12.10a` - `ios_xe = 16.12.11` - `ios_xe = 16.12.12` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **cisco-sa-hardening-iosxe-V8NMuMZJ** · Cisco · affected: Cisco IOS XE Software (595 versions) · updated 2026-08-05 · [advisory](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxe-V8NMuMZJ)