Security readout for executives and security teams
Plain-English summary
CVE-2021-1621 can let someone on the same network segment disrupt a Cisco IOS XE router interface. The issue affects availability, not data theft or alteration. Business urgency is highest where IOS XE devices face shared, campus, provider, or otherwise untrusted Layer 2 networks.
Executive priority
Treat this as a high-priority availability risk for network infrastructure, especially in environments with shared local network access. It is not evidenced as actively exploited in the provided sources, but a successful attack could interrupt routing on affected interfaces.
Technical view
Cisco describes improper handling in IOS XE Layer 2 punt code. An unauthenticated adjacent attacker could send specific Layer 2 frames that wedge an interface queue, causing denial of service. CVSS 3.1 is 7.4 with adjacent access, low complexity, no privileges, and high availability impact.
Likely exposure
Exposure is limited to Cisco IOS XE Software devices reachable by an attacker on the same Layer 2 segment. The source bundle does not provide exact affected releases, so teams must verify product and version applicability against Cisco’s advisory.
Exploitation context
The provided sources support adjacent, unauthenticated exploitation for denial of service. They do not show internet-remote exploitation, confidentiality impact, integrity impact, or active exploitation. The bundle marks CISA KEV status as false.
Researcher notes
Key constraints are adjacent attack surface and availability-only impact. The bundle lacks affected version detail and explicit fix text, so validation depends on Cisco’s advisory. Avoid assuming broader product impact or active exploitation without additional source evidence.
Mitigation direction
- Review Cisco’s advisory for affected releases, fixed software, and workarounds.
- Inventory Cisco IOS XE devices on shared or untrusted Layer 2 segments.
- Prioritize remediation for routing interfaces exposed to less trusted local networks.
- Reduce unnecessary Layer 2 adjacency to critical IOS XE interfaces where feasible.
- Monitor Cisco and CVE sources for advisory updates.
Validation and detection
- Confirm whether each Cisco IOS XE device matches Cisco’s affected-release criteria.
- Map which IOS XE interfaces are reachable from shared Layer 2 segments.
- Check monitoring for interface queue wedge, traffic drops, or unexplained DoS symptoms.
- Verify remediation decisions are documented against Cisco advisory guidance.
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-399: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-1621 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/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:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H2.84Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.4HighVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210922 Cisco IOS XE Software Interface Queue Wedge 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.
Resource Management Errors
Resource Management Errors represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.