#VU31418 Reachable Assertion in Tor - CVE-2017-0376

Vulnerability identifier: #VU31418

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2017-0376

CWE-ID: CWE-617

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Tor
Client/Desktop applications / Web browsers

Vendor: tor.eff.org

Description

The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.

The hidden-service feature in Tor before 0.3.0.8 allows a denial of service (assertion failure and daemon exit) in the connection_edge_process_relay_cell function via a BEGIN_DIR cell on a rendezvous circuit.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Tor: 0.3.0.0 - 0.3.0.7

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External links
https://www.debian.org/security/2017/dsa-3877
https://github.com/torproject/tor/commit/56a7c5bc15e0447203a491c1ee37de9939ad1dcd
https://lists.torproject.org/pipermail/tor-announce/2017-June/000131.html
https://trac.torproject.org/projects/tor/ticket/22494

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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.