Google Details Two Zero-Click Bugs in Zoom Clients That Let Attackers Execute Malicious Code

Two zero-click bugs in Zoom clients have been detected recently by the security analyst Natalie Silvanovich of Google’s Project Zero that enables the threat actors to execute malicious code.

By exploiting these security flaws, the attackers target the:-

  • Zoom clients
  • Multimedia Router (MMR) servers

With the help of these two elements, the audio and video content between clients is transmitted. While after patching them, the company has recently activated the ASLR. 

On successful exploitation of these two zero-click bugs, the threat actors can achieve control over the device of their victim that also without any kind of interaction from the user end.

Flaw Profile

  • CVE ID: CVE-2021-34423
  • Description: A buffer overflow vulnerability that can be leveraged to crash the service or application or execute arbitrary code.
  • CVSS score: 9.8
  • Severity: Critical
  • CVE ID: CVE-2021-34424
  • Description: A process memory exposure flaw that could be used to potentially gain insight into arbitrary areas of the product’s memory.
  • CVSS score: 7.5
  • Severity: High


An attacker can manipulate the contents of a buffer by exploiting these bugs, and this could be executed by sending a malformed chat message to crash the client and MMR server.

Not only that even, by joining a Zoom meeting via a web browser, it is also possible to leak data from memory, and this happens due to the lack of a NULL check. 

Here’s what the security expert, Natalie Silvanovich stated:-

“The lack of ASLR in the Zoom MMR process greatly increased the risk that an attacker could compromise it. ASLR is arguably the most important mitigation in preventing exploitation of memory corruption, and most other mitigations rely on it on some level to be effective. There is no good reason for it to be disabled in the vast majority of software.”

Zoom has a closed nature, and its closed nature greatly affected this investigation. Since most of the video conferencing systems use the open-source software:-

  • WebRTC

These open-source software platforms are not bug-free, but since they are open-source, so, they could be easily rectified by vendors and analysts.

Moreover, one of the most interesting key features of zero-click attacks, they don’t leave any footprints or traces of any malicious activity; in short, they create such a complexity due to which it becomes very difficult to detect them.

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POOJA is a Passionate Security Enthusiast, CEH, ECSA, ISO 27001 Lead auditor, Ex-PCI-AQSA, CISSP, Security Researcher, Security blogger, and Author at GBHackers On Security.

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