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Vulnerability record · CVE-2008-5523 · published 12 December 2008

CVE-2008-5523: Avast antivirus improper input validation vulnerability

Avast · Avast Antivirus

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.

9.3 CVSS 2.0 High EPSS 2.9% · top 13.6% CWE-20 · Improper input validation
9.3CVSS 2.0 base score
2.9%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References
16 Jun 2026Last modified by NVD

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.

AV:N/AC:M/Au:N/C:C/I:C/A:C

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://securityreason.com/securityalert/4723
http://www.securityfocus.com/archive/1/498995/100/0/threaded
http://www.securityfocus.com/archive/1/499043/100/0/threaded
https://exchange.xforce.ibmcloud.com/vulnerabilities/47435
http://securityreason.com/securityalert/4723
http://www.securityfocus.com/archive/1/498995/100/0/threaded
http://www.securityfocus.com/archive/1/499043/100/0/threaded
https://exchange.xforce.ibmcloud.com/vulnerabilities/47435

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2008-5523), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.