Vulnerability identifier: #VU7479

Vulnerability risk: Low

CVSSv3.1: 4.6 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2017-0377

CWE-ID: CWE-384

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Tor
Client/Desktop applications / Web browsers

Vendor: tor.eff.org

Description
The vulnerability allows a remote unauthenticated user to hijack the target user's session.

The weakness exists due to guard-selection algorithm only considers the exit relay (not the exit relay's family). A remote attacker can leverage the existence of large families, defeat intended anonymity properties and steal the victim's session.

Mitigation
Update to version 0.3.0.9.

Vulnerable software versions

Tor: 0.3.0.0 - 0.3.0.8

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External links
http://trac.torproject.org/projects/tor/ticket/22753
http://blog.torproject.org/blog/tor-0309-released-security-update-clients

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Q & A

Can this vulnerability be exploited remotely?

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

Is there known malware, which exploits this vulnerability?

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