1) Double Free

Risk: Critical

CVSSv3.1: 8.4 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C] [PCI]

CVE-ID: CVE-2021-26411

CWE-ID: CWE-415 - Double Free

Exploit availability: No

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary error when processing ".mht" files. A remote attacker can trick the victim to visit a specially crafted webpage, trigger a double free error and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Note, the vulnerability is being actively exploited in the wild.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Microsoft Internet Explorer: 9, 10, 11

CPE

• cpe:2.3:a:microsoft:microsoft_internet_explorer:11:*:*:*:*::*:*
• cpe:2.3:a:microsoft:microsoft_internet_explorer:10:*:*:*:*::*:*
• cpe:2.3:a:microsoft:microsoft_internet_explorer:9:*:*:*:*::*:*

External links

https://enki.co.kr/blog/2021/02/04/ie_0day.html
https://twitter.com/dnpushme/status/1357264755333816320
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26411

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?

Yes. This vulnerability is being exploited in the wild.