Vulnerability identifier: #VU26506

Vulnerability risk: Medium

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

CVE-ID: CVE-2020-10593

CWE-ID: CWE-401

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Tor
Client/Desktop applications / Web browsers

Vendor: tor.eff.org

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

The vulnerability exists due to memory leak in "circpad_setup_machine_on_circ" because a circuit-padding machine can be negotiated twice on the same circuit. A remote attacker can cause a denial of service condition on the target system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Tor: 0.3.5.0 - 0.4.2.6

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External links
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00045.html
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00052.html
http://security.gentoo.org/glsa/202003-50
http://trac.torproject.org/projects/tor/ticket/33619

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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.