Security readout for executives and security teams
Plain-English summary
This flaw can let an unauthenticated remote attacker disrupt management access to an affected Cisco Small Business switch by abusing IPv6 traffic handling. It affects availability, not data theft or tampering. IPv4 traffic is not affected, so urgency depends on whether these switches process IPv6 traffic in your environment.
Executive priority
Treat this as a moderate availability risk. It is unlikely to expose data, but it can disrupt switch management, especially at sites relying on remote administration. Prioritize validation where IPv6 is used and where loss of management access would delay operations or incident response.
Technical view
CVE-2020-3496 is an insufficient input validation issue in the IPv6 packet processing engine of Cisco Small Business Smart and Managed Switches. A crafted IPv6 packet passing through an affected device can cause the switch management CLI to stop responding, creating a denial-of-service condition. CVSS is 5.3 with network attack vector and no privileges required.
Likely exposure
Exposure is most likely where Cisco Small Business 250 Series Smart Switches Software is deployed and IPv6 traffic can traverse the device. The source bundle does not provide affected version ranges, CPEs, or fixed-release details. IPv4-only paths are outside the described impact.
Exploitation context
The source bundle says KEV is false and provides no evidence of active exploitation. The issue is remotely reachable over the network, requires low attack complexity, and needs no authentication, but the stated impact is limited to management CLI availability.
Researcher notes
The provided evidence identifies CWE-20, IPv6-specific packet validation failure, and CLI denial of service. Version detail is incomplete in the bundle, so validation should rely on Cisco’s advisory rather than assumptions. Avoid treating IPv4 exposure as affected based on the provided description.
Mitigation direction
- Review the Cisco advisory for affected releases and vendor-recommended fixes.
- Inventory Cisco Small Business 250 Series switches and software versions.
- Assess whether IPv6 traffic traverses affected switches.
- Prioritize remediation for exposed management-critical or remote-site switches.
- Monitor affected devices for management CLI availability issues.
Validation and detection
- Confirm deployed switch models and software against the Cisco advisory.
- Verify whether IPv6 is enabled or routed through these switches.
- Check operational logs for management CLI hangs or availability incidents.
- Track remediation status for each affected switch asset.
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-20: 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-2020-3496 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
- Medium
- CVSS
- 5.3 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
5.3MediumVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- 20200819 Cisco Small Business Smart and Managed Switches 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.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.