CVE-2005-3303: The FSG unpacker (fsg.c) in Clam AntiVirus (ClamAV) 0.80 through 0.87 allows remote attackers to cause "memory

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HIGH 7.5DOWNGRADE

CVE-2005-3303 is a high-severity flaw (CVSS 7.5) affecting clamav. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The FSG unpacker (fsg.c) in Clam AntiVirus (ClamAV) 0.80 through 0.87 allows remote attackers to cause "memory corruption" and execute arbitrary code via a crafted FSG 1.33 file.

Why this priority

High severity
EPSS top 6%: very likely to be exploited

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	6.9% (top 6%)
CISA exploited list	No
Published	2005-11-05
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

2005-11-05 11:02 UTCPublished CVE record published
2026-06-16 22:16 UTCUpdated Record last modified

clam anti-virus clamav DOWNGRADE

Affected: 0.80 · 0.81 · 0.82 · 0.83 · 0.84 · 0.85 · 0.85.1 · 0.86

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.80

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.80 (Debian / Ubuntu)

apt-cache madison clamav sudo apt install clamav=<VERSION_BEFORE_0.80> sudo apt-mark hold clamav

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

dnf --showduplicates list clamav sudo dnf downgrade clamav-<VERSION_BEFORE_0.80> 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-2005-3303?

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

Is CVE-2005-3303 being exploited?

CVE-2005-3303 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-2005-3303 affect?

CVE-2005-3303 affects clamav. Severity is high (CVSS 7.5). The FSG unpacker (fsg.c) in Clam AntiVirus (ClamAV) 0.80 through 0.87 allows remote attackers to cause "memory corruption" and execute arbitrary code via a crafted FSG 1.33 file.

How urgent is CVE-2005-3303?

Priority 50/100. High severity; EPSS top 6%: very likely to be exploited

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References

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