CVE-2021-34761: Cisco Firepower Threat Defense Software CLI Arbitrary File Write Vulnerability

Severity: medium (CVSS 6.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-10-27 · updated 2026-08-11
Weakness: CWE-73

Description

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.

Affected products

Cisco Firepower Management Center Virtual Appliance: 6.2.3, 6.4.0, 6.6.1, 6.7.0, 7.0.0, 7.1.0
Cisco Firepower Threat Defense Software: from 6.4.0 before 6.4.0.13; from 6.6.0 before 6.6.5; from 6.7.0 before 6.7.0.3; from 7.0.0 before 7.0.1 — fixed in 6.4.0.13, 6.6.5, 6.7.0.3, 7.0.1
Cisco Sourcefire Defense Center: 6.2.3, 6.4.0, 6.6.1, 6.7.0, 7.0.0, 7.1.0

How to fix

Upgrade to a fixed version: Cisco Firepower Threat Defense Software 6.4.0.13, 6.6.5, 6.7.0.3, 7.0.1. Check the vendor advisory for mitigations.

References

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