(Pwn2Own) Zoom Heap based Buffer Overflow Remote Code Execution Vulnerability

August 17th, 2021
ZDI-21-971 ZDI-CAN-13587

CVE ID

CVE-2021-34407

CVSS Score

7.3 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Affected Vendors

Zoom

Affected Products

Client

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Zoom Clients. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the processing of encrypted messages. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length heap-based buffer. An attacker can leverage this vulnerability to execute code in the context of the current user.

Additional Details

Zoom has issued an update to correct this vulnerability. More details can be found at:
https://explore.zoom.us/en/trust/security/security-bulletin/

Disclosure Timeline

  • 2021-04-07 - Vulnerability reported to vendor
  • 2021-08-17 - Coordinated public release of advisory

Credit

Daan Keuper and Thijs Alkemade from Computest

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