CVE-2008-5521: Avira AntiVir 7.9.0.36 and possibly 7.8.1.28, when Internet Explorer 6 or 7 is used, allows remote attackers t

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HIGH 9.3DOWNGRADE

CVE-2008-5521 is a high-severity flaw (CVSS 9.3) affecting antivir. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Avira AntiVir 7.9.0.36 and possibly 7.8.1.28, 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.

Why this priority

Critical severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.3 (High)
EPSS exploit chance	1.9% (top 20%)
CISA exploited list	No
Weakness	CWE-20
Published	2008-12-12
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: free-av

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2008-12-12 18:30 UTCPublished CVE record published
2026-06-16 23:00 UTCUpdated Record last modified

free-av antivir DOWNGRADE

Affected: 7.8.1.28 · 7.9.0.36

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.8.1.28

1. Check installed version

apt-cache policy antivir || rpm -q antivir || antivir --version

2. No fixed release: DOWNGRADE to a release before 7.8.1.28 (Debian / Ubuntu)

apt-cache madison antivir sudo apt install antivir=<VERSION_BEFORE_7.8.1.28> sudo apt-mark hold antivir

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list antivir sudo dnf downgrade antivir-<VERSION_BEFORE_7.8.1.28> sudo dnf versionlock add antivir

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2008-5521?

antivir: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2008-5521 being exploited?

CVE-2008-5521 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2008-5521 affect?

CVE-2008-5521 affects antivir. Severity is high (CVSS 9.3). Avira AntiVir 7.9.0.36 and possibly 7.8.1.28, 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 fil

How urgent is CVE-2008-5521?

Priority 52/100. Critical severity

Software pages

Internet Explorer vulnerabilities

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References

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