CVE-2026-20274: As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XR Software eng

This month

CRITICAL 9.8REMOTEMITIGATE

CVE-2026-20274 is a critical-severity flaw (CVSS 9.8) affecting ios xr. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XR Software engineering team has conducted a comprehensive internal security review. This review resulted in a software hardening releases that address multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20274 are related to improper resource control issues that are grouped under the Common Weakness Enumeration (CW

Why this priority

Critical severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Weakness	CWE-664
Published	2026-09-02
Last modified	2026-09-17

Publisher (CNA): Cisco Systems, Inc. · Vendor: cisco

Last updated 2026-09-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-02 17:17 UTCPublished CVE record published
2026-09-17 18:03 UTCUpdated Record last modified

cisco ios xr MITIGATE

Affected: 6.5.25 · 6.5.26 · 6.5.28 · 6.5.29 · 6.5.31 · 6.5.32 · 6.5.33 · 6.5.35

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.5.25

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Advisories and coverage

Official advisories

Cisco Security Advisories: Cisco IOS XR Software Security Hardening Release: September 2026 2026-09-17

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-20274?

ios xr: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-20274 being exploited?

CVE-2026-20274 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-20274 affect?

CVE-2026-20274 affects ios xr. Severity is critical (CVSS 9.8). As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XR Software engineering team has conducted a comprehensive internal security review. This review resulted in a software hardening releases that a

How urgent is CVE-2026-20274?

Priority 50/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

iOS vulnerabilities · Cisco vulnerabilities

Related CVEs

CVE-2026-20280 HIGH 8.8 MITIGATE As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XR Softwar
CVE-2026-20276 HIGH 8.6 MITIGATE As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XR Software eng

References

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