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Fencer Intel
high 8.8

CVE-2021-40420 json

A use-after-free vulnerability exists in the JavaScript engine of Foxit Software’s PDF Reader, version 11.1.0.52543.

published 4y ago modified 4mo ago also EUVD-2021-27597

cvss
8.8
version 3.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
4.7%
EPSS 4.7% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known

Summary

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.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
last yr.

Exploit prediction

4.69% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • talosintelligence.com https://talosintelligence.com/vulnerability_reports/TALOS-2021-1429 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.0 8.8 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • n/a Foxit

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.