CVE-2021-34699Network attack vector

Authenticated device reload via web-to-CLI parser interaction

Published Sep 23, 2021 · Updated Nov 18, 2024

Denial of service in the TrustSec CLI parser in Cisco IOS allows remote authenticated users to reload affected devices through the web UI. The web UI passes a particular CLI command to the TrustSec parser, where improper interaction between the components triggers the reload. Exploitation requires a vulnerable release on a TrustSec-capable device with the web UI enabled and interrupts service by rebooting the device.

CVSS severity7.7
High
EPSS probability1.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the TrustSec CLI parser in Cisco IOS allows remote authenticated users to reload affected devices through the web UI. The web UI passes a particular CLI command to the TrustSec parser, where improper interaction between the components triggers the reload. Exploitation requires a vulnerable release on a TrustSec-capable device with the web UI enabled and interrupts service by rebooting the device.

The record

CVE
CVE-2021-34699
Published
Sep 23, 2021
Updated
Nov 18, 2024
Vendor
ClamAV
Product
Cisco IOS
Classifications
CWE-435, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 18, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ClamAV · Cisco IOSversion=n/a

Published CVSS scores

7.7CiscoCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-435Improper Interaction Between Multiple Correctly-Behaving Entities
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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