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CVE-2021-34761

Cisco Firepower Threat Defense Software CLI Arbitrary File Write Vulnerability

4.4 Medium

A vulnerability in Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite or append arbitrary data to system files using root-level privileges. The attacker must have administrative credentials on the device. This vulnerability is due to incomplete validation of user input for a specific CLI command. An attacker could exploit this vulnerability by authenticating to the device with administrative privileges and issuing a CLI command with crafted user parameters. A successful exploit could allow the attacker to overwrite or append arbitrary data to system files using root-level privileges.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
High
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
None

Exploit likelihood

0.22%Unchanged since Oct 28, 2021
90%50%10%1%

What each source reports

CVE List Score used 4.4

Cisco Firepower Threat Defense Software CLI Arbitrary File Write Vulnerability

A vulnerability in Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite or append arbitrary data to system files using root-level privileges. The attacker must have administrative credentials on the device. This vulnerability is due to incomplete validation of user input for a specific CLI command. An attacker could exploit this vulnerability by authenticating to the device with administrative privileges and issuing a CLI command with crafted user parameters. A successful exploit could allow the attacker to overwrite or append arbitrary data to system files using root-level privileges.

Record
CVE-2021-34761
CVSS 3.1
4.4 MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
Weakness
CWE-73
Updated
2026-11-02
EUVDEUVD-2021-21411 4.4

A vulnerability in Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite or append arbitrary data to system files using root-level privileges. The attacker must have administrative credentials on the device. This vulnerability is due to incomplete validation of user input for a specific CLI command. An attacker could exploit this vulnerability by authenticating to the device with administrative privileges and issuing a CLI command with crafted user parameters. A successful exploit could allow the attacker to overwrite or append arbitrary data to system files using root-level privileges.

Record
EUVD-2021-21411
CVSS 3.1
4.4 MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
Updated
2026-11-03
GitHub AdvisoriesGHSA-3vcw-92x2-jjg4 6.0

A vulnerability in Cisco Firepower Threat Defense (FTD) Software could allow an authenticated,...

A vulnerability in Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite or append arbitrary data to system files using root-level privileges. The attacker must have administrative credentials on the device. This vulnerability is due to incomplete validation of user input for a specific CLI command. An attacker could exploit this vulnerability by authenticating to the device with administrative privileges and issuing a CLI command with crafted user parameters. A successful exploit could allow the attacker to overwrite or append arbitrary data to system files using root-level privileges.

Record
GHSA-3vcw-92x2-jjg4
CVSS 3.1
6.0 MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-20, CWE-73, CWE-668
Updated
2026-11-02
NVD 4.4

A vulnerability in Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite or append arbitrary data to system files using root-level privileges. The attacker must have administrative credentials on the device. This vulnerability is due to incomplete validation of user input for a specific CLI command. An attacker could exploit this vulnerability by authenticating to the device with administrative privileges and issuing a CLI command with crafted user parameters. A successful exploit could allow the attacker to overwrite or append arbitrary data to system files using root-level privileges.

Record
CVE-2021-34761
CVSS 3.1
4.4 MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
CVSS 3.1
6.0 MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
CVSS 2.0
6.6 MediumAV:L/AC:L/Au:N/C:N/I:C/A:C
Weakness
CWE-73, CWE-668
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
aliases, publishedEUVD
first indexedCVE List, GitHub Advisories, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-34761 is a medium vulnerability (CVSS 4.4) in Cisco Firepower Threat Defense Software, published October 27, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 12th percentile. No source names a fixed version.

References

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