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Fencer Vulns
high 7.8

CVE-2021-45338 json

Multiple privilege escalation vulnerabilities in Avast Antivirus prior to 20.4 allow a local user to gain elevated privileges by calling un…

published 2021-12-27 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-32111

cvss
7.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

Multiple privilege escalation vulnerabilities in Avast Antivirus prior to 20.4 allow a local user to gain elevated privileges by calling unnecessarily powerful internal methods of the main antivirus service which could lead to the (1) arbitrary file delete, (2) write and (3) reset security.

Patch / fix

  • avast antivirus 20.4

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/the-deniss/Vulnerability-Disclosures/tree/main/CVE-2021-AVST1.1 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/the-deniss/Vulnerability-Disclosures/tree/main/CVE-2021-AVST1.2 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/the-deniss/Vulnerability-Disclosures/tree/main/CVE-2021-AVST1.3 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

References

Sources

Fencer Vulns 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.