Security readout for executives and security teams
Plain-English summary
This is a denial-of-service issue in Cisco IOS and IOS XE Software. A logged-in remote user with access to the web UI could trigger a CLI parser interaction that reloads the device, interrupting network service. The supplied sources do not identify active exploitation.
Executive priority
Prioritize internet- or broadly reachable management interfaces first. The business risk is service outage on network infrastructure, not confidentiality loss. Treat as high priority for network operations if affected Cisco devices expose web UI access beyond tightly controlled admins.
Technical view
The vulnerability is in the TrustSec CLI parser interaction with the web UI. CVSS 3.1 is 7.7, with network attack vector, low complexity, low privileges, no user interaction, changed scope, and high availability impact. The source bundle does not provide affected version ranges or fixed release details.
Likely exposure
Exposure is most likely where Cisco IOS or IOS XE devices run affected software and expose the web UI to authenticated users. The supplied bundle does not specify affected versions, device models, or configurations beyond TrustSec CLI parser and web UI involvement.
Exploitation context
The bundle supports an authenticated remote denial-of-service scenario, not unauthenticated compromise or data theft. KEV status is false, and no provided source states active exploitation. Successful exploitation would cause a device reload and service disruption.
Researcher notes
Do not assume exploitability across all Cisco IOS or IOS XE deployments. The supplied evidence lacks version ranges, model details, fixed releases, and workaround specifics. Validation should anchor on Cisco’s advisory and local device inventory.
Mitigation direction
- Review Cisco advisory for affected releases and fixed software.
- Upgrade or patch according to Cisco guidance where applicable.
- Restrict web UI access to trusted management networks and administrators.
- Review administrator and low-privilege accounts with web UI access.
- Monitor for unexpected reloads on potentially affected devices.
Validation and detection
- Inventory Cisco IOS and IOS XE devices with web UI enabled.
- Compare running software versions against Cisco advisory guidance.
- Identify accounts permitted to use the web UI.
- Review logs for unexpected reloads or administrative web UI activity.
- Confirm management interfaces are not broadly reachable.
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-435: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-34699 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
- 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 and IOS XE Software TrustSec CLI Parser 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 Interaction Between Multiple Correctly-Behaving Entities
Improper Interaction Between Multiple Correctly-Behaving Entities represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.