CVE-2021-40420: foxit pdf_reader Use After Free

Vulnerability summary

CVE-2021-40420 is a high (CVSS 8.8) Use After Free vulnerability in foxit pdf_reader. EPSS estimates a 4.69% chance of exploitation in the next 30 days, higher than 91.6% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 04-02-2022
   PublishedVulnerability first disclosed.
2. 15-04-2025
   Last modifiedVulnerability information updated.

Description

A use-after-free vulnerability exists in the JavaScript engine of Foxit Software’s PDF Reader, version 11.1.0.52543. A specially-crafted PDF document can trigger the reuse of previously freed memory, which can lead to arbitrary code execution. An attacker needs to trick the user to open the malicious file to trigger this vulnerability. Exploitation is also possible if a user visits a specially-crafted, malicious site if the browser plugin extension is enabled.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.