CVE-2001-1581: The File Blocker feature in Clearswift MAILsweeper for SMTP 4.2 allows remote attackers to bypass e-mail attac

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HIGH 7.5DOWNGRADE

CVE-2001-1581 is a high-severity flaw (CVSS 7.5) affecting mailsweeper. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The File Blocker feature in Clearswift MAILsweeper for SMTP 4.2 allows remote attackers to bypass e-mail attachment filtering policies via a modified name in a Content-Type header.

Why this priority

High severity

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	1.3% (top 30%)
CISA exploited list	No
Published	2001-12-31
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: clearswift limited

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

Am I affected?

Timeline

2001-12-31 05:00 UTCPublished CVE record published
2026-06-16 21:56 UTCUpdated Record last modified

clearswift limited mailsweeper DOWNGRADE

Affected: 4.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.2

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.2 (Debian / Ubuntu)

apt-cache madison mailsweeper sudo apt install mailsweeper=<VERSION_BEFORE_4.2> sudo apt-mark hold mailsweeper

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

dnf --showduplicates list mailsweeper sudo dnf downgrade mailsweeper-<VERSION_BEFORE_4.2> sudo dnf versionlock add mailsweeper

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-2001-1581?

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

Is CVE-2001-1581 being exploited?

CVE-2001-1581 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-2001-1581 affect?

CVE-2001-1581 affects mailsweeper. Severity is high (CVSS 7.5). The File Blocker feature in Clearswift MAILsweeper for SMTP 4.2 allows remote attackers to bypass e-mail attachment filtering policies via a modified name in a Content-Type header.

How urgent is CVE-2001-1581?

Priority 44/100. High severity

Related CVEs

CVE-2004-2328 MEDIUM 5.0 DOWNGRADE Clearswift MAILsweeper for SMTP before 4.3_13 allows remote attackers to cause a denial of service (infinite l
CVE-2004-0235 MEDIUM 6.4 DOWNGRADE DOWNGRADE Multiple directory traversal vulnerabilities in LHA 1.14 allow remote attackers or local users to create arbit
CVE-2004-0234 HIGH 10.0 DOWNGRADE DOWNGRADE Multiple stack-based buffer overflows in the get_header function in header.c for LHA 1.14, as used in products
CVE-2004-0162 HIGH 7.5 DOWNGRADE DOWNGRADE Multiple content security gateway and antivirus products allow remote attackers to bypass content restrictions
CVE-2004-0161 HIGH 7.5 DOWNGRADE DOWNGRADE Multiple content security gateway and antivirus products allow remote attackers to bypass content restrictions

References

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