How severe is CVE-2021-45339?

CVE-2021-45339 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-45339 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (23rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-45339?

CVE-2021-45339 affects Avast Antivirus. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-45339?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-45339 published?

CVE-2021-45339 was published on 2021-12-27 and last updated on 2026-06-17.

CVE-2021-45339

CVE-2021-45339 is a high-severity vulnerability in Avast Antivirus with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-863.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 7.2
EPSS exploit prediction: 0% (23rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Avast Antivirus
Published: 2021-12-27
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-45339?: 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.
How severe is CVE-2021-45339?: CVE-2021-45339 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-45339 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (23rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-45339?: CVE-2021-45339 affects Avast Antivirus. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-45339?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-45339 published?: CVE-2021-45339 was published on 2021-12-27 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:avast:antivirus:*:*:*:*:*:*:*:*

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