CVE-2006-6406: Clam AntiVirus (ClamAV) 0.88.6 allows remote attackers to bypass virus detection by inserting invalid characte

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MEDIUM 5.0DOWNGRADE

CVE-2006-6406 is a medium-severity flaw (CVSS 5.0) affecting clamav. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Clam AntiVirus (ClamAV) 0.88.6 allows remote attackers to bypass virus detection by inserting invalid characters into base64 encoded content in a multipart/mixed MIME file, as demonstrated with the EICAR test file.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	3.3% (top 12%)
CISA exploited list	No
Published	2006-12-10
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: clam anti-virus

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

Am I affected?

Timeline

2006-12-10 02:28 UTCPublished CVE record published
2026-06-16 22:33 UTCUpdated Record last modified

clam anti-virus clamav DOWNGRADE

Affected: 0.88.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.88.6

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.88.6 (Debian / Ubuntu)

apt-cache madison clamav sudo apt install clamav=<VERSION_BEFORE_0.88.6> sudo apt-mark hold clamav

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

dnf --showduplicates list clamav sudo dnf downgrade clamav-<VERSION_BEFORE_0.88.6> sudo dnf versionlock add clamav

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-2006-6406?

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

Is CVE-2006-6406 being exploited?

CVE-2006-6406 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-2006-6406 affect?

CVE-2006-6406 affects clamav. Severity is medium (CVSS 5.0). Clam AntiVirus (ClamAV) 0.88.6 allows remote attackers to bypass virus detection by inserting invalid characters into base64 encoded content in a multipart/mixed MIME file, as demonstrated with the EICAR test file.

How urgent is CVE-2006-6406?

Priority 45/100. Public exploit reference

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References

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