CVE-2021-34761
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.
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
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 Medium
CVSS: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 Medium
CVSS: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 Medium
CVSS: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 Medium
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N - CVSS 3.1
- 6.0 Medium
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H - CVSS 2.0
- 6.6 Medium
AV:L/AC:L/Au:N/C:N/I:C/A:C - Weakness
- CWE-73, CWE-668
- 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-2021-34761 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.