Security readout for executives and security teams
Plain-English summary
This vulnerability can make affected Cisco IOS or IOS XE devices reload when handling certain DNS resolution activity through Split DNS. The business impact is availability: routing or network services may briefly go down or become unstable if an exposed device is triggered.
Executive priority
Treat as a high-priority availability risk for Cisco network infrastructure using Split DNS. Prioritize exposed or business-critical devices, but avoid assuming compromise or active exploitation from the provided evidence.
Technical view
CVE-2020-3408 is a Split DNS denial-of-service issue in Cisco IOS and IOS XE. Cisco describes a regex engine timeout while processing DNS name list configuration. An unauthenticated remote attacker can trigger affected handling of an address or hostname, causing device reload and availability loss.
Likely exposure
Exposure is likely limited to Cisco IOS or IOS XE devices running affected releases with Split DNS enabled. The source bundle does not provide affected version ranges, so teams need Cisco advisory confirmation against their inventory.
Exploitation context
The bundle reports network-reachable, low-complexity, unauthenticated exploitation leading to device reload. It does not show CISA KEV listing or cited evidence of active exploitation in the wild.
Researcher notes
The advisory-backed mechanism is regex processing timeout in Split DNS name list handling, mapped to CWE-185. Version and fix details are not present in the bundle, so validation depends on Cisco’s advisory and local configuration evidence.
Mitigation direction
- Identify Cisco IOS and IOS XE devices using Split DNS.
- Review Cisco’s advisory for affected releases, fixed software, and vendor workarounds.
- Prioritize remediation for devices reachable by untrusted DNS resolution paths.
- Monitor affected devices for unexpected reloads until remediation is complete.
Validation and detection
- Check inventory for Cisco IOS and IOS XE devices.
- Confirm whether Split DNS is configured on those devices.
- Compare installed software releases with Cisco’s advisory.
- Review device logs for unexpected reloads or DNS-related instability.
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-185: 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-2020-3408 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 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/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:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.6HighVector: CVSS:3.0/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 and IOS XE Software Split DNS 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.
Incorrect Regular Expression
Incorrect Regular Expression represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.