Foxit Reader Vulnerability Let Hackers Run Malicious Code via PDFs

Aleksander Nikolic, the security expert of Cisco Talos has recently detected a vulnerability that is continuously targeting the “Foxit Reader.”

However, Foxit has already published an update, so that they can close this severe vulnerability which is allowing attackers to exploit the PDFs to run malicious code remotely.  

The security experts have detected many security holes, but they are still investigating the whole matter. The specialists have named the vulnerability “CVE-2021-21822,” and they are still trying to find out the key details of this vulnerability.

This vulnerability is one of the high severity remote code execution, and it has been allowing the threat actors to implement malicious code on a user’s Windows computer remotely so that they can take control over the device.

After digging more about this vulnerability the analysts found that 650 million users from nearly 200 countries are currently using its reader.

Not only this but the list also includes large enterprise customers like Google, Intel, NASDAQ, Dell, Chevron, Asus, British Airways, HP, and Lenovo.

Flaw profile

  • CVE: CVE-2021-21822
  • CWE: CWE-416 – Use After Free
  • CVSS: 8.8
  • Severity: Critical

Users Exposed to RCE Attacks Due to’Use After Free’ Bug

The cybersecurity analyst, Aleksander Nikolic from Cisco Talos has detected this severe flaw through the “Use After Free” bug. 

Nikolic found this flaw in the V8 JavaScript engine, and this V8 engine is used by Foxit Reader to display the dynamic forms and communicative document elements.

Due to the improper handling of annotations by the Foxit Reader application and its browser extension this type of vulnerability occurs. And here the attacker takes the advantage of these annotations to craft malicious PDFs, that are later used to run an arbitrary code on the device.

More Bugs Were Fixed

This is not the first time when Foxit Reader gets attacked, as there are various other security bugs that are continuously attacking the former version of the  Foxit Reader.

All the security bugs were revealing users’ devices to the denial services, information disclosure, DLL hijacking, remote code execution, SQL injection, and many other security bugs.

Here are the security fixes that Foxit Reader has fixed in its 10.1.4 version:-

  • Memory Corruption vulnerability
  • Denial of Service vulnerability
  • Null Pointer Reference, Out-of-Bounds Read, Context Level Bypass, Type Confusion, or Buffer Overflow vulnerability 
  • Arbitrary File Deletion vulnerability
  • Deliver incorrect signature information
  • DLL Hijacking vulnerability
  • Read Remote Code Execution vulnerability
  • Information Disclosure vulnerability
  • Out-of-Bounds Write vulnerability
  • Arbitrary File Write Remote Code Execution vulnerability
  • SQL Injection Remote Code Execution vulnerability
  • Uninitialized Variable Information Disclosure vulnerability
  • Heap-based Buffer Overflow vulnerability


Apart from all these things, this vulnerability class the Foxit Reader as well as its former versions as well. And according to the report, it was being addressed with the release of Foxit Reader

However, the researchers have strongly recommended the users of Foxit Reader to immediately update their software with the new version. And to do so, you have to follow the simple steps that we have mentioned below:-

  • First, you have to open the app.
  • Then click on the “Check for Updates” in the app’s “Help” dialog.
  • That’s it, your update procedure will start.

So, following or implementing the above steps will provide greater security and consequently, the users will be able to keep themselves safe and secure from this kind of security bug.

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