CVE-2021-34699
Cisco IOS and IOS XE Software TrustSec CLI Parser Denial of Service Vulnerability
A vulnerability in the TrustSec CLI parser of Cisco IOS and Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload. This vulnerability is due to an improper interaction between the web UI and the CLI parser. An attacker could exploit this vulnerability by requesting a particular CLI command to be run through the web UI. A successful exploit could allow the attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Cisco IOS and IOS XE Software TrustSec CLI Parser Denial of Service Vulnerability
A vulnerability in the TrustSec CLI parser of Cisco IOS and Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload. This vulnerability is due to an improper interaction between the web UI and the CLI parser. An attacker could exploit this vulnerability by requesting a particular CLI command to be run through the web UI. A successful exploit could allow the attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
- Record
CVE-2021-34699- CVSS 3.1
- 7.7 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H - Weakness
- CWE-435
- Updated
- 2026-11-02
EUVDEUVD-2021-21349
A vulnerability in the TrustSec CLI parser of Cisco IOS and Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload. This vulnerability is due to an improper interaction between the web UI and the CLI parser. An attacker could exploit this vulnerability by requesting a particular CLI command to be run through the web UI. A successful exploit could allow the attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
- Record
EUVD-2021-21349- CVSS 3.1
- 7.7 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-6q78-w5mw-hqpj
A vulnerability in the TrustSec CLI parser of Cisco IOS and Cisco IOS XE Software could allow an...
A vulnerability in the TrustSec CLI parser of Cisco IOS and Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload. This vulnerability is due to an improper interaction between the web UI and the CLI parser. An attacker could exploit this vulnerability by requesting a particular CLI command to be run through the web UI. A successful exploit could allow the attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
- Record
GHSA-6q78-w5mw-hqpj- CVSS 3.1
- 7.7 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H - Weakness
- CWE-435, CWE-436
- Updated
- 2026-11-02
NVD
A vulnerability in the TrustSec CLI parser of Cisco IOS and Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload. This vulnerability is due to an improper interaction between the web UI and the CLI parser. An attacker could exploit this vulnerability by requesting a particular CLI command to be run through the web UI. A successful exploit could allow the attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
- Record
CVE-2021-34699- CVSS 3.1
- 7.7 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H - CVSS 2.0
- 6.8 Medium
AV:N/AC:L/Au:S/C:N/I:N/A:C - Weakness
- CWE-435, CWE-436
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-34699 is a high vulnerability (CVSS 7.7) in Cisco Ios, published September 23, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.19%, the 68th percentile. No source names a fixed version.