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CVE-2018-7300: Eq 3 Homematic Ccu2 Firmware: Path traversal

CVE-2018-7300 is rated critical with a CVSS v3.1 base score of 9.8 and NVD lists Eq 3 Homematic Ccu2 Firmware as the affected product. Per its scoring, it can be exploited over the network, without authentication, without any user interaction. The scored impact on confidentiality, integrity and availability is the highest available.

Vulnerability description

Directory Traversal / Arbitrary File Write / Remote Code Execution in the User.setLanguage method in eQ-3 AG Homematic CCU2 2.29.2 and earlier allows remote attackers to write arbitrary files to the device's filesystem. This vulnerability can be exploited by unauthenticated attackers with access to the web interface.

Severity breakdown

CVSS v3.1 9.8: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
Attack complexity: Low. No special conditions; the attack can be repeated reliably.
Privileges required: None. No account or prior access is needed.
User interaction: None. No action from any user is needed.
Scope: Unchanged. Impact stays within the vulnerable component.
Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
Availability impact: High. Total loss of availability; the component can be shut down.

Underlying weakness

CWE-22: Improper Limitation of a Pathname to a Restricted Directory

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Affected products

Eq 3 Homematic Ccu2 Firmware: up to and including 2.29.22