Remote code execution in Microsoft Excel



Published: 2021-06-08 | Updated: 2021-06-14
Risk High
Patch available YES
Number of vulnerabilities 1
CVE ID CVE-2021-31939
CWE ID CWE-416
Exploitation vector Network
Public exploit Public exploit code for vulnerability #1 is available.
Vulnerable software
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Office Online Server
Server applications / Other server solutions

Microsoft Office
Client/Desktop applications / Office applications

Microsoft Excel
Client/Desktop applications / Office applications

Microsoft Office Web Apps Server
Server applications / Application servers

Vendor Microsoft

Security Advisory

This security advisory describes one high risk vulnerability.

1) Use-after-free

Risk: High

CVSSv3.1: 7.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C] [PCI]

CVE-ID: CVE-2021-31939

CWE-ID: CWE-416 - Use After Free

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a use-after-free error when processing Excel files. A remote attacker can create a specially crafted Excel file, trick the victim into opening it, trigger a use-after-free error and execute arbitrary code on the system.

Successful exploitation of the vulnerability may allow an attacker to compromise vulnerable system.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Office Online Server : 2016

Microsoft Office: 2013, 2013 RT, 2016, 2019

Microsoft Excel: 2013, 2013 RT Service Pack 1, 2016

Microsoft Office Web Apps Server: 2013 Service Pack 1

CPE External links

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31939
https://www.zerodayinitiative.com/advisories/ZDI-21-670/

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.



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