Cisco IOS XR Software Security Hardening Release: September 2026

criticalCVE-2026-20274 CVE-2026-20275 CVE-2026-20276 CVE-2026-20277 CVE-2026-20278 CVE-2026-20279

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 software hardening releases that address multiple internally discovered vulnerabilities. These vulnerabilities were found during internal testing and are not known to be actively exploited. To assist customers in patching and streamline the disclosure process, Cisco has grouped these issues by their underlying vulnerability class — Common Weakness Enumeration (CWE) — and assigned a single Common Vulnerabilities and Exposures identifier (CVE ID) to each CWE grouping. Cisco has released software updates that address these vulnerabilities. There are no workarounds that address these vulnerabilities. This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxr-qg64NcM Security Impact Rating: Critical CVE: CVE-2026-20274,CVE-2026-20275,CVE-2026-20276,CVE-2026-20277,CVE-2026-20278,CVE-2026-20279,CVE-2026-20280

CSIRTS triage

vendor: Cisco product: IOS XR Software Remote code execution Privilege escalation Memory corruptionOther

What: Multiple internally discovered vulnerabilities grouped by CWE and assigned single CVE identifiers, addressed through security hardening releases.
Who is affected: Cisco IOS XR Software deployments across all affected versions.
Urgency: Critical; no active exploitation known but comprehensive internal security review identified multiple high-risk flaws requiring immediate patching.
Action: Apply Cisco security hardening releases addressing CVE-2026-20274 through CVE-2026-20280 without delay.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Cisco Security Advisories (INTL · vendor-psirt · site)
Severity: critical
Published: 2026-09-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxr-qg64NcM?vs_f=Cisco%20Security%20Advisory%26vs_cat=Security%20Intelligence%26vs_type=RSS%26vs_p=Cisco%20IOS%20XR%20Software%20Security%20Hardening%20Release:%20September%202026%26vs_k=1

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-202740.67% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 50% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-202750.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-202760.25% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 17% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-202770.22% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 12% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-202780.28% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 21% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-202790.28% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 21% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-202800.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 19% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-20274	coverage & exploitation status	NVD · CVE.org
CVE-2026-20275	coverage & exploitation status	NVD · CVE.org
CVE-2026-20276	coverage & exploitation status	NVD · CVE.org
CVE-2026-20277	coverage & exploitation status	NVD · CVE.org
CVE-2026-20278	coverage & exploitation status	NVD · CVE.org
CVE-2026-20279	coverage & exploitation status	NVD · CVE.org
CVE-2026-20280	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Cisco IOS XR

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownNCSC-2026-0338 [1.00] [M/H] Kwetsbaarheden verholpen in Cisco Nexus 9000 Series, IOS XR Software en Secure Ema…ncsc-nl · 2026-09-03
high[NEW] [high] Cisco IOS XR: Multiple vulnerabilities enable unspecified attackcert-bund · 2026-09-03
highCVE-2026-20280: As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS…nvd · 2026-09-02
criticalCVE-2026-20279: As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS…nvd · 2026-09-02
highCVE-2026-20278: As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS…nvd · 2026-09-02
highCVE-2026-20277: As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS…nvd · 2026-09-02