Security readout for executives and security teams
Plain-English summary
This flaw can let an unauthenticated remote attacker crash and reload affected Cisco Catalyst 9800 wireless controllers by sending crafted CAPWAP traffic. The business impact is wireless service disruption, not data theft or system takeover, based on the provided sources.
Executive priority
Treat this as a high-priority availability risk for sites dependent on Cisco Catalyst 9800 wireless controllers. It warrants prompt inventory and upgrade planning, especially where wireless uptime supports revenue, operations, or safety-critical workflows.
Technical view
CVE-2020-3399 is a Cisco IOS XE CAPWAP packet-processing issue affecting Cisco Catalyst 9800 Series Wireless Controllers. Insufficient input validation can trigger a buffer over-read, causing device crash and reload. CVSS 3.1 is 8.6 with network access, low complexity, no privileges, no user interaction, and high availability impact.
Likely exposure
Exposure is most relevant where Cisco Catalyst 9800 Series Wireless Controllers process CAPWAP traffic reachable from untrusted or poorly segmented networks. The bundle does not provide exact affected IOS XE versions, so version validation must rely on Cisco’s advisory.
Exploitation context
The provided sources describe unauthenticated remote exploitation for denial of service. They do not state active exploitation, public exploit availability, or CISA KEV listing; KEV is false in the supplied bundle.
Researcher notes
The root issue is CWE-126 buffer over-read in CAPWAP processing. The impact is crash and reload rather than confidentiality or integrity loss. The source bundle lacks exact vulnerable version ranges and fixed-release details, so avoid assumptions beyond Cisco advisory validation.
Mitigation direction
- Review the Cisco advisory for affected and fixed IOS XE release guidance.
- Upgrade affected controllers according to Cisco’s recommended fixed software guidance.
- Restrict CAPWAP reachability to trusted wireless infrastructure where architecture permits.
- Monitor controller crash, reload, and CAPWAP-related fault events.
- Prioritize resilient wireless controller design for critical sites.
Validation and detection
- Inventory Cisco Catalyst 9800 Series Wireless Controllers running IOS XE.
- Compare running software versions against Cisco’s advisory guidance.
- Confirm CAPWAP exposure is limited to expected access point networks.
- Review controller logs for unexplained crashes or reloads.
- Verify wireless availability monitoring covers controller reload events.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-126: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2020-3399 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.6HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20200924 Cisco IOS XE Wireless Controller Software for the Catalyst 9000 Family CAPWAP Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Buffer Over-read
Buffer Over-read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.