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
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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

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-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

External links

http://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

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-2021-28090

CWE-ID: CWE-617 - Reachable Assertion

Exploit availability: No

Description

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

The vulnerability exists due to a reachable assertion in servers configured as directory authorities. A remote attacker can send specially crafted data to the server, trigger an assertions failure and crash it.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Tor: 0.3.5.0 - 0.4.5.6

External links

http://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.



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