Security readout for executives and security teams
Plain-English summary
CVE-2021-40122 can let an unauthenticated remote attacker disrupt Cisco Meeting Server calls. If exploited, the Call Bridge device may reload, dropping active meetings. The business impact is service interruption, not data theft or system takeover, based on the provided sources.
Executive priority
Treat as a moderate availability risk for organizations dependent on Cisco Meeting Server. Prioritize review if conferencing supports customer-facing, executive, healthcare, legal, or incident-response workflows where dropped calls create operational disruption.
Technical view
The vulnerability is in a Cisco Meeting Server Call Bridge API and stems from improper handling of large series of message requests. Successful exploitation can trigger a device reload and denial of service. CVSS 3.1 is 5.9: network reachable, unauthenticated, high attack complexity, availability impact only.
Likely exposure
Exposure is most likely in organizations running Cisco Meeting Server where the Call Bridge API is reachable by untrusted networks. The source bundle does not provide affected version ranges, fixed versions, or CPEs, so version-specific exposure must be confirmed against Cisco guidance.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Publicly provided details indicate denial-of-service potential only. Attack complexity is rated high, which lowers likelihood but does not remove risk for internet-reachable conferencing infrastructure.
Researcher notes
Evidence is limited to the CVE record and Cisco advisory reference. The bundle confirms unauthenticated remote DoS, Call Bridge API involvement, CWE-399, and CVSS 5.9. It does not include affected version ranges, exploit observations, workaround details, or fixed release names.
Mitigation direction
- Review Cisco advisory for affected and fixed release details.
- Inventory Cisco Meeting Server deployments and Call Bridge exposure.
- Restrict untrusted network reachability to management or API surfaces where feasible.
- Schedule Cisco-recommended updates if your deployed version is affected.
- Monitor for unexplained Call Bridge reloads or dropped calls.
Validation and detection
- Confirm whether Cisco Meeting Server is deployed in the environment.
- Identify enabled Call Bridge services and exposed API interfaces.
- Compare deployed versions against Cisco advisory guidance.
- Review availability logs for reloads around call-drop incidents.
- Verify compensating network controls limit untrusted API access.
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
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-2021-40122 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
- 5.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/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:H/PR:N/UI:N/S:U/C:N/I:N/A:H2.23.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.9MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20211020 Cisco Meeting Server Call Bridge 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.