Security readout for executives and security teams
Plain-English summary
CVE-2021-1623 can let an authenticated remote user disrupt Cisco cBR-8 broadband routers by overwhelming SNMP handling. The business impact is service availability: affected routers may enter a denial-of-service condition. The source bundle does not provide affected version ranges or named fixed releases.
Executive priority
Treat as high priority for broadband infrastructure where cBR-8 routers support customer-facing services. The risk is outage, not data theft, but availability impact can be material.
Technical view
The flaw is in SNMP punt handling on Cisco IOS XE Software for Cisco cBR-8 Converged Broadband Routers. Large quantities of SNMP requests can overwhelm the punt path. Exploitation requires network access and low privileges, needs no user interaction, and affects availability only per the CVSS vector.
Likely exposure
Exposure is likely limited to organizations operating Cisco cBR-8 Converged Broadband Routers with IOS XE where SNMP is enabled and reachable by authenticated remote users.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation is described as authenticated and remote, using large volumes of SNMP requests to trigger denial of service.
Researcher notes
Evidence supports an authenticated remote DoS via SNMP punt path exhaustion. The bundle lacks exact affected versions, fixed versions, and operational mitigations from the advisory text, so validation should rely on Cisco’s authoritative advisory.
Mitigation direction
- Check Cisco advisory for affected releases and official remediation guidance.
- Restrict SNMP access to trusted management networks and hosts.
- Review SNMP users, communities, and least-privilege configuration.
- Monitor for abnormal SNMP request volumes and router availability degradation.
- Prioritize remediation for internet-adjacent or broadly reachable management planes.
Validation and detection
- Inventory Cisco cBR-8 routers and their IOS XE software versions.
- Confirm whether SNMP is enabled on each device.
- Verify SNMP reachability is limited to approved management sources.
- Review logs and monitoring for SNMP spikes or DoS symptoms.
- Compare exact device versions against Cisco’s 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
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CWE-399: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-1623 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/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:L/UI:N/S:C/C:N/I:N/A:H3.14Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.7HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210922 Cisco IOS XE Software for Cisco cBR-8 Converged Broadband Routers Simple Network Management Protocol 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.