Cisco IOS vulnerabilities: known CVEs & security history
Cisco · Network / Security · 11 tracked CVEs · 2 actively exploited · updated September 2026 · what is a CVE? →
This is the full list of known vulnerabilities (CVEs) across all Cisco IOS release lines — 11 in total, with 2 actively exploited in the wild. A CVE here doesn't mean your version is affected — check Cisco IOS's current status and the safe version to run.
Known Cisco IOS CVEs
Actively-exploited and most-severe first. Open any CVE for full details.
| CVE | Severity | CVSS | EPSS | Year |
|---|---|---|---|---|
| CVE-2008-4128⚡ exploited | high | 8.1 | 34% | 2008 |
| CVE-2025-20352⚡ exploited | high | 7.7 | 39% | 2025 |
| CVE-2025-20363 | critical | 9 | 8% | 2025 |
| CVE-2026-20301 | high | 8.6 | 0% | 2026 |
| CVE-2026-20012 | high | 8.6 | 0% | 2026 |
| CVE-2025-20160 | high | 8.1 | 0% | 2025 |
| CVE-2025-20327 | high | 7.7 | 0% | 2025 |
| CVE-2023-20081 | medium | 6.8 | 1% | 2023 |
| CVE-2025-20149 | medium | 6.5 | 0% | 2025 |
| CVE-2020-3315 | medium | 5.3 | 2% | 2020 |
| CVE-2000-0984 | medium | 5 | 4% | 2000 |
Is my Cisco IOS version affected?
The list above spans every release. To know whether your version is affected — and the minimum safe version to upgrade to — check it directly.
Check your Cisco IOS version → · Monitor Cisco IOS for new CVEs →
Cisco IOS vulnerabilities — frequently asked
How many known vulnerabilities does Cisco IOS have?
IsItPatched tracks 11 CVEs for Cisco IOS, 2 of which are actively exploited (CISA KEV). 1 is critical-severity and 6 high-severity. These span every release line — what matters is whether the version you run is affected.
Does Cisco IOS have any actively-exploited vulnerabilities?
Yes — 2 Cisco IOS CVEs are in CISA's Known Exploited Vulnerabilities catalog, meaning they are confirmed exploited in the wild. Patch these as a priority.
What is the most severe Cisco IOS vulnerability?
Among tracked issues, CVE-2008-4128 (HIGH, CVSS 8.1), which is actively exploited, ranks highest — a Cross-site request forgery (CSRF) weakness.
Is Cisco IOS safe to use?
It depends on the version. The latest supported Cisco IOS release clears the known issues; older versions may still be affected. Check the exact version you run for a verdict.
CVE data aggregated from NVD, CISA KEV and EPSS (FIRST.org). Related: Cisco IOS security status · Cisco IOS end-of-life · actively-exploited CVEs. Always verify against Cisco's advisories — see our disclaimer.