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.

Published: 2021-10-27 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-34761 is rated Low Risk (30.8/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.16%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-34761

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.05% 0.16% +0.11%
2 2025-11-18 0.18% 0.05% -0.13%
3 2025-03-17 — 0.18% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-34761

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.4 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 0.8 3.6 [email protected]
6.0 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 0.8 5.2 [email protected]
6.6 2.0 MEDIUM
AV:L/AC:L/Au:N/C:N/I:C/A:C Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 3.9 9.2 [email protected]

Weakness enumeration for CVE-2021-34761

Affected software / configurations for CVE-2021-34761

Vendor Product Version Raw CPE
cisco firepower_management_center_virtual_appliance 6.2.3 cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.2.3:*:*:*:*:*:*:*
cisco firepower_management_center_virtual_appliance 6.4.0 cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.4.0:*:*:*:*:*:*:*
cisco firepower_management_center_virtual_appliance 6.6.1 cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.6.1:*:*:*:*:*:*:*
cisco firepower_management_center_virtual_appliance 6.7.0 cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.7.0:*:*:*:*:*:*:*
cisco firepower_management_center_virtual_appliance 7.0.0 cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:7.0.0:*:*:*:*:*:*:*
cisco firepower_management_center_virtual_appliance 7.1.0 cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:7.1.0:*:*:*:*:*:*:*
cisco firepower_threat_defense >= 6.4.0, < 6.4.0.13 cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
cisco firepower_threat_defense >= 6.6.0, < 6.6.5 cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
cisco firepower_threat_defense >= 6.7.0, < 6.7.0.3 cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
cisco firepower_threat_defense >= 7.0.0, < 7.0.1 cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
cisco sourcefire_defense_center 6.2.3 cpe:2.3:a:cisco:sourcefire_defense_center:6.2.3:*:*:*:*:*:*:*
cisco sourcefire_defense_center 6.4.0 cpe:2.3:a:cisco:sourcefire_defense_center:6.4.0:*:*:*:*:*:*:*
cisco sourcefire_defense_center 6.6.1 cpe:2.3:a:cisco:sourcefire_defense_center:6.6.1:*:*:*:*:*:*:*
cisco sourcefire_defense_center 6.7.0 cpe:2.3:a:cisco:sourcefire_defense_center:6.7.0:*:*:*:*:*:*:*
cisco sourcefire_defense_center 7.0.0 cpe:2.3:a:cisco:sourcefire_defense_center:7.0.0:*:*:*:*:*:*:*
cisco sourcefire_defense_center 7.1.0 cpe:2.3:a:cisco:sourcefire_defense_center:7.1.0:*:*:*:*:*:*:*

References for CVE-2021-34761

cvelogic Threat Intelligence