Input validation error in tor.eff Tor

1) Input validation error

EUVDB-ID: #VU38653

Risk: Medium

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2017-11565

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote non-authenticated attacker to manipulate data.

debian/tor.init in the Debian tor_0.2.9.11-1~deb9u1 package for Tor was designed to execute aa-exec from the standard system pathname if the apparmor package is installed, but implements this incorrectly (with a wrong assumption that the specific pathname would remain the same forever), which allows attackers to bypass intended AppArmor restrictions by leveraging the silent loss of this protection mechanism. NOTE: this does not affect systems, such as default Debian stretch installations, on which Tor startup relies on a systemd unit file (instead of this tor.init script).

Mitigation

Install update from vendor's website.

Vulnerable software versions

Tor: 0.2.9.11-1

External links

http://www.securityfocus.com/bid/99933
http://bugs.debian.org/869153

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to visit a specially crafted website.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.