Exploited CVEs / Cisco / CVE-2020-3118
CVE-2020-3118
Cisco IOS XR Software Discovery Protocol Format String Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2022-05-03 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Cisco Security Advisories (PSIRT), linked below.
Actively exploited Cisco IOS XR vulnerability, High severity, CVSS 8.8. Added to the CISA KEV catalog 2021-11-03.
Risk summary
Updated July 27, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2020-3118
This is a format string flaw in how Cisco IOS XR parses Cisco Discovery Protocol fields, so an unauthenticated attacker on an adjacent Layer 2 segment can run code with admin privileges or crash the device by reloading it. CDP is enabled by default on many interfaces, meaning any exposed IOS XR router or switch reachable at the link layer is at risk. CISA confirmed active exploitation and added it to KEV on 2021-11-03, and with Severity High (CVSS 8.8) the adjacent access requirement is the only real barrier.
Do this: Patch affected Cisco IOS XR devices now, and where patching lags, disable CDP on untrusted or edge-facing interfaces to remove the attack surface.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2020-3118
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2020-3118
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
CISA required action
Federal (BOD 22-01) remediation due date: 2022-05-03 (past due).
Apply updates per vendor instructions.
Official fix for CVE-2020-3118
The authoritative fix and affected-version list are published by the vendor. Find the IOS XR advisory on Cisco Security Advisories (PSIRT).
Common questions about CVE-2020-3118
Is CVE-2020-3118 actively exploited?
Yes. CVE-2020-3118 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 12%.
What is the CISA deadline and required action for CVE-2020-3118?
CISA set the federal (BOD 22-01) remediation due date at 2022-05-03, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.
What fixes CVE-2020-3118?
The authoritative fix is in the vendor advisory: see Cisco Security Advisories (PSIRT) for the patched IOS XR versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.
Can I ask my own AI about CVE-2020-3118?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2020-3118's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).
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