How severe is CVE-2026-27749?

CVE-2026-27749 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-2026-27749 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-27749?

CVE-2026-27749 affects Avira Internet Security. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-27749?

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.

Does CVE-2026-27749 have an EU (EUVD) identifier?

Yes. CVE-2026-27749 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9821.

When was CVE-2026-27749 published?

CVE-2026-27749 was published on 2026-03-05 and last updated on 2026-06-17.

CVE-2026-27749

CVE-2026-27749 is a high-severity vulnerability in Avira Internet Security 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-502.

Key facts

Severity: High (CVSS 3.x base score 7.8)
EPSS exploit prediction: 0% (24th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-9821
Weakness: CWE-502
Affected product: Avira Internet Security
Published: 2026-03-05
Last modified: 2026-06-17

Description

Avira Internet Security contains a deserialization of untrusted data vulnerability in the System Speedup component. The Avira.SystemSpeedup.RealTimeOptimizer.exe process, which runs with SYSTEM privileges, deserializes data from a file located in C:\\ProgramData using .NET BinaryFormatter without implementing input validation or deserialization safeguards. Because the file can be created or modified by a local user in default configurations, an attacker can supply a crafted serialized payload that is deserialized by the privileged process, resulting in arbitrary code execution as SYSTEM.

Frequently asked questions

What is CVE-2026-27749?: Avira Internet Security contains a deserialization of untrusted data vulnerability in the System Speedup component. The Avira.SystemSpeedup.RealTimeOptimizer.exe process, which runs with SYSTEM privileges, deserializes data from a file located in C:\\ProgramData using .NET BinaryFormatter without implementing input validation or deserialization safeguards. Because the file can be created or modified by a local user in default configurations, an attacker can supply a crafted serialized payload that is deserialized by the privileged process, resulting in arbitrary code execution as SYSTEM.
How severe is CVE-2026-27749?: CVE-2026-27749 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-2026-27749 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-27749?: CVE-2026-27749 affects Avira Internet Security. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-27749?: 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.
Does CVE-2026-27749 have an EU (EUVD) identifier?: Yes. CVE-2026-27749 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-9821.
When was CVE-2026-27749 published?: CVE-2026-27749 was published on 2026-03-05 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:avira:internet_security:*:*:*:*:*:windows:*:*

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