Multiple vulnerabilities in Tor

Published: 2021-03-17

Risk	Medium
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2021-28089 CVE-2021-28090
CWE-ID	CWE-400 CWE-617
Exploitation vector	Network
Public exploit	N/A
Vulnerable software	Tor Client/Desktop applications / Web browsers
Vendor	tor.eff.org

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Resource exhaustion

EUVDB-ID: #VU51541

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-2021-28089

CWE-ID: CWE-400 - Resource exhaustion

Exploit availability: No

Description

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

The vulnerability exists due to application does not properly control consumption of internal resources when processing directory data. A remote attacker can force the Tor instance do consume huge amounts of CPU resources and perform a denial of service (DoS) attack.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Tor: 0.3.5.0 - 0.4.5.6

CPE2.3

External links

https://blog.torproject.org/node/2009

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.

2) Reachable Assertion

EUVDB-ID: #VU51542