CVE-2020-3399: Cisco IOS XE Wireless Controller Software for the Catalyst 9000 Family CAPWAP Denial of Service Vulnerability
Telemetry drift only. No threshold crossed and no authority ruling changed.
CVE record, CISA KEV and EPSS as of 2026-10-18.
CVEs like this one computed, by meaning
What to do now held facts and links
- No fix version is held. The CNA's first reference is the place to look: tools.cisco.com
- Record your decision, dated and frozen with today's evidence: patch by a date · mitigated by a compensating control · deferred · accepted the risk · not affected
- Check your version against the ranges this record publishes.
What it is stated by the CNA
A vulnerability in the Control and Provisioning of Wireless Access Points (CAPWAP) protocol processing of Cisco IOS XE Software for Cisco Catalyst 9800 Series Wireless Controllers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition of an affected device. The vulnerability is due to insufficient input validation during CAPWAP packet processing. An attacker could exploit this vulnerability by sending a crafted CAPWAP packet to an affected device, resulting in a buffer over-read. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition on the affected device.
- weakness
- CWE-126
- affected
- Cisco IOS XE Software
- published ranges
- cisco ios xe 16.12; cisco ios xe 16.12.1s; cisco ios xe 16.12.2
- fixed in
- No fix version in held sources.
- severity
- 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- assigned by
- cisco
- published
- 2020-09-24
check us tools.cisco.com
Exploit code held, dated
- exploit code
- None held in the PoC-in-GitHub feed. A public repository changes this brief.
What moved held, dated
| date | EPSS | event |
|---|---|---|
| 14 Apr 2021 | 0.00651 | |
| 6 Jan 2022 | 0.02857 | |
| 4 Feb 2022 | 0.04499 | |
| 1 Apr 2022 | 0.01055 | |
| 7 Mar 2023 | 0.00138 | scoring model v2023.03.01 |
| 1 May 2023 | 0.0014 | |
| 10 Jun 2023 | 0.0016 | |
| 17 Mar 2025 | 0.00564 | scoring model v2025.03.14 |
| 29 Mar 2025 | 0.00761 | |
| 30 Mar 2025 | 0.00564 | |
| 15 Jun 2026 | 0.01345 | scoring model v2026.06.15 |
| 19 Jun 2026 | 0.01361 |
12 observations held. A step marked with a scoring model moved because the measurement was replaced, not because the vulnerability changed.
Outside the record researched, cited
This section reads the record's references and adds cited findings from outside it. It needs an account. Everything above is held facts and is complete without it.
What would change this brief held, dated
- CISA KEV
- Not listed in the catalogue we hold. A listing changes this brief.
- exploit probability
- 0.01 on 2026-06-19 (FIRST's EPSS, a probability and not evidence of exploitation). Next band line: 10% (0.10). Crossing a line changes this brief.
- fix
- No fix version is held. One published by the CNA or OSV changes this brief.
How to check this
Every value above is held with two dates: when it was true upstream (as_of) and when we recorded it (tx_from). Re-derive the exploit probability as it stood on any date:
SELECT value, source, source_version, as_of, tx_from
FROM volatile_valid_as_of('CVE-2020-3399', '2026-10-29T23:59:59.999999Z', now());