How severe is CVE-2008-5523?

CVE-2008-5523 has a CVSS 2.0 base score of 9.3, rated critical severity.

Is CVE-2008-5523 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2008-5523?

CVE-2008-5523 affects Avast Avast Antivirus. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2008-5523?

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

When was CVE-2008-5523 published?

CVE-2008-5523 was published on 2008-12-12 and last updated on 2026-06-16.

CVE-2008-5523

CVE-2008-5523 is a critical-severity vulnerability in Avast Avast Antivirus with a CVSS 2.0 base score of 9.3. 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-20.

Key facts

Severity: Critical (CVSS 2.0 base score 9.3)
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Avast Avast Antivirus
Published: 2008-12-12
Last modified: 2026-06-16

Description

avast! antivirus 4.8.1281.0, when Internet Explorer 6 or 7 is used, allows remote attackers to bypass detection of malware in an HTML document by placing an MZ header (aka "EXE info") at the beginning, and modifying the filename to have (1) no extension, (2) a .txt extension, or (3) a .jpg extension, as demonstrated by a document containing a CVE-2006-5745 exploit.

Frequently asked questions

What is CVE-2008-5523?: avast! antivirus 4.8.1281.0, when Internet Explorer 6 or 7 is used, allows remote attackers to bypass detection of malware in an HTML document by placing an MZ header (aka "EXE info") at the beginning, and modifying the filename to have (1) no extension, (2) a .txt extension, or (3) a .jpg extension, as demonstrated by a document containing a CVE-2006-5745 exploit.
How severe is CVE-2008-5523?: CVE-2008-5523 has a CVSS 2.0 base score of 9.3, rated critical severity.
Is CVE-2008-5523 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2008-5523?: CVE-2008-5523 affects Avast Avast Antivirus. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2008-5523?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2008-5523 published?: CVE-2008-5523 was published on 2008-12-12 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:avast:avast_antivirus:4.8.1281.0:*:*:*:*:*:*:*

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