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CVE-2017-8805: Debian Ftpsync: Path traversal

CVE-2017-8805 is rated critical with a CVSS v3.0 base score of 9.1 and affects Debian Ftpsync. Per its scoring, it can be exploited over the network, without authentication, without any user interaction.

Vulnerability description

Debian ftpsync before 20171017 does not use the rsync --safe-links option, which allows remote attackers to conduct directory traversal attacks via a crafted upstream mirror.

Severity breakdown

CVSS v3.0 9.1: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

• 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: None. No effect on availability.

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

• Debian Ftpsync: up to and including 20171016

References

• http://www.openwall.com/lists/oss-security/2017/10/17/2
• https://anonscm.debian.org/cgit/mirror/archvsync.git/commit/?id=d1ca2ab2210990b6dfb664cd6776a41b71c48016
• https://lists.debian.org/debian-mirrors/2017/10/msg00017.html