TI-2021-20490 Aliases CVE-2021-45339 GHSA-4j2p-j8c6-h5p8

Privilege escalation vulnerability in Avast Antivirus prior to 20.4 allows a local user…

LOW 34CWE-863Published 2021-12-27 · Updated 2024-08-04

Key facts

Attack vector: Local
Privileges required: Low
User interaction: None
Attack complexity: Low
Impact type: Security bypass
Confidentiality · integrity · availability: High · High · High
Fix status: No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-863.

Summary

Privilege escalation vulnerability in Avast Antivirus prior to 20.4 allows a local user to gain elevated privileges by "hollowing" trusted process which could lead to the bypassing of Avast self-defense.

Why it matters now

EPSS 0.00327 25th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
—	—	all versions	—	No fix listed	CNA

— Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:avast:antivirus::::::::	before 20.4	Vulnerable	Avast

cpe:2.3:a:avast:antivirus:*:*:*:*:*:*:*:* Versions before 20.4 Vulnerable ·Avast

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2021-45339
2026-10-03 Alias added: GHSA-4j2p-j8c6-h5p8

References

Exploit 1

https://github.com/the-deniss/Vulnerability-Disclosures/tree/main/CVE-2021-AVST0

Advisory 1

https://www.avast.com/hacker-hall-of-fame/en/researcher-david-eade-reports-antitrack-bug-to-avast-0

TI-2020-08753 An issue was discovered in Avast Antivirus before 20. CVSS 3.1CRITICAL 9.8
TI-2017-05872 In Avast Antivirus before v17, using the LPC interface API exposed by the AvastSVC.exe… CVSS 3.0CRITICAL 9.8
TI-2025-03074 Integer Overflow in Avast Antiviurs 25.1.981.6 on Windows may result in privilege escalation CVSS 3.1CRITICAL 9.8
TI-2025-11929 Time-of-check time-of-use race condition in Avast Antivirus CVSS 3.1CRITICAL 9.9
TI-2021-20488 Privilege escalation vulnerability in the Self-Defense driver of Avast Antivirus prior to… CVSS 3.1HIGH 8.8
TI-2021-20487 Privilege escalation vulnerability in the Sandbox component of Avast Antivirus prior to… CVSS 3.1HIGH 8.8

See all 31 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences