CVE-1999-1521: Computalynx CMail 2.4 and CMail 2.3 SP2 SMTP servers are vulnerable to a buffer overflow attack in the MAIL FR

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HIGH 10.0DOWNGRADE

CVE-1999-1521 is a high-severity flaw (CVSS 10.0) affecting cmail. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Computalynx CMail 2.4 and CMail 2.3 SP2 SMTP servers are vulnerable to a buffer overflow attack in the MAIL FROM command that may allow a remote attacker to execute arbitrary code on the server.

Why this priority

Critical severity
EPSS top 5%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	8.1% (top 5%)
CISA exploited list	No
Published	1999-09-12
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: computalynx

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

Am I affected?

Timeline

1999-09-12 04:00 UTCPublished CVE record published
2026-06-16 21:50 UTCUpdated Record last modified

computalynx cmail DOWNGRADE

Affected: 2.3sp2 · 2.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.3sp2

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.3sp2 (Debian / Ubuntu)

apt-cache madison cmail sudo apt install cmail=<VERSION_BEFORE_2.3sp2> sudo apt-mark hold cmail

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

dnf --showduplicates list cmail sudo dnf downgrade cmail-<VERSION_BEFORE_2.3sp2> sudo dnf versionlock add cmail

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: Computalynx CMail 2.3 SP2/2.4 - SMTP Buffer Overflow

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-1999-1521?

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

Is CVE-1999-1521 being exploited?

CVE-1999-1521 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-1999-1521 affect?

CVE-1999-1521 affects cmail. Severity is high (CVSS 10.0). Computalynx CMail 2.4 and CMail 2.3 SP2 SMTP servers are vulnerable to a buffer overflow attack in the MAIL FROM command that may allow a remote attacker to execute arbitrary code on the server.

How urgent is CVE-1999-1521?

Priority 64/100. Critical severity; EPSS top 5%: very likely to be exploited; Public exploit reference

Related CVEs

CVE-2001-0742 HIGH 7.5 DOWNGRADE Buffer overflow in Computalynx CMail POP3 mail server 2.4.9 allows remote attackers to run arbitrary code via
CVE-2000-0557 HIGH 10.0 DOWNGRADE Buffer overflow in the web interface for Cmail 2.4.7 allows remote attackers to execute arbitrary commands via
CVE-2000-0556 MEDIUM 5.0 DOWNGRADE Buffer overflow in the web interface for Cmail 2.4.7 allows remote attackers to cause a denial of service by s

References

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