CVE-2026-20277

HIGH 8.2 ALL-YEARS

Published 2026-09-02 · Last modified 2026-09-18 · cisco · NVD: Awaiting Analysis

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-2026-20277 are related to protection mechanism failure issues that are grouped under the Common Weakness Enumeration (CWE) CWE-693.

ELEVATED IMPACT

Severe if exploited (CVSS 8.2), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.4%chance of exploitation in 30 days · 35th percentile

○ In CISA KEV○ Catalogued PoC◆ SSVC: exploitation none, automatable yes

Impact if exploited

8.2CVSS 3.1 · HIGH · CNA

ConfidentialityNone
IntegrityLow
AvailabilityHigh

What an attacker needs

✓Access: Reachable over the network — no local access needed
✓Privileges: No account or privileges required
✓User interaction: No user interaction needed
✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

Search GitHub now — results may be empty or unverified.

Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Affected

Vendors Cisco

Products Cisco Ios Xr Software

Weakness (CWE)

CWE-693: Protection Mechanism Failure

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

References and research data (JSON)

All CVSS metrics

HIGH 8.2 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
HIGH 8.2 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

References

Advisories

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-70202 ADVISORYEUVD · EUVD-2026-70202

Technical & other

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-iosxr-qg64NcMCVE record · cisco · Updated 2026-09-18T12:10:19.569Z
NVD · CVE-2026-20277 · Updated 2026-09-18T13:17:28.387
https://www.cve.org/Media/News/item/blog/2026/06/16/Preserving-Vulnerability-Level-IdentificationCVE record · CVE · Updated 2026-09-15T17:03:58.628Z
NVD · CVE-2026-20277 · Updated 2026-09-18T13:17:28.387

Sources: NVD · CVE.org · All sources and attribution · EPSS