Vulnerability identifier: #VU31388

Vulnerability risk: High

CVSSv3.1: 7.1 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2017-8823

CWE-ID: CWE-416

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 execute arbitrary code.

In Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9, there is a use-after-free in onion service v2 during intro-point expiration because the expiring list is mismanaged in certain error cases, aka TROVE-2017-013.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Tor: 0.3.1 - 0.3.1.8

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External links
http://blog.torproject.org/new-stable-tor-releases-security-fixes-0319-03013-02914-02817-02516
http://bugs.torproject.org/24313
http://bugs.torproject.org/24430
http://www.debian.org/security/2017/dsa-4054

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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.