CVE-2003-1177: Buffer overflow in the base64 decoder in MERCUR Mailserver 4.2 before SP3a allows remote attackers to cause a

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HIGH 7.5DOWNGRADE

CVE-2003-1177 is a high-severity flaw (CVSS 7.5) affecting mercur mailserver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in the base64 decoder in MERCUR Mailserver 4.2 before SP3a allows remote attackers to cause a denial of service and possibly execute arbitrary code via a long (1) AUTH command to the POP3 server or (2) AUTHENTICATE command to the IMAP server.

Why this priority

High severity
EPSS top 4%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	12.9% (top 4%)
CISA exploited list	No
Published	2003-12-31
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: atrium software

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

Am I affected?

Timeline

2003-12-31 05:00 UTCPublished CVE record published
2026-06-16 22:03 UTCUpdated Record last modified

atrium software mercur mailserver DOWNGRADE

Affected: 3.3 · 3.3_sp1 · 3.3_sp2 · 4.1 · 4.1_sp1 · 4.2 · 4.2_sp1 · 4.2_sp2

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.3

1. Check installed version

apt-cache policy mercur-mailserver || rpm -q mercur-mailserver || mercur-mailserver --version

2. No fixed release: DOWNGRADE to a release before 3.3 (Debian / Ubuntu)

apt-cache madison mercur-mailserver sudo apt install mercur-mailserver=<VERSION_BEFORE_3.3> sudo apt-mark hold mercur-mailserver

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

dnf --showduplicates list mercur-mailserver sudo dnf downgrade mercur-mailserver-<VERSION_BEFORE_3.3> sudo dnf versionlock add mercur-mailserver

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: Atrium Software Mercur MailServer 3.3/4.0/4.2 - IMAP AUTH Remote 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-2003-1177?

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

Is CVE-2003-1177 being exploited?

CVE-2003-1177 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-2003-1177 affect?

CVE-2003-1177 affects mercur mailserver. Severity is high (CVSS 7.5). Buffer overflow in the base64 decoder in MERCUR Mailserver 4.2 before SP3a allows remote attackers to cause a denial of service and possibly execute arbitrary code via a long (1) AUTH command to the POP3 server or (2) AUTHENTICATE command t

How urgent is CVE-2003-1177?

Priority 55/100. High severity; EPSS top 4%: very likely to be exploited; Public exploit reference

Related CVEs

CVE-2003-1322 HIGH 10.0 UPGRADE Multiple stack-based buffer overflows in Atrium MERCUR IMAPD in MERCUR Mailserver before 4.2.15.0 allow remote
CVE-2002-1073 HIGH 7.5 DOWNGRADE Buffer overflow in the control service for MERCUR Mailserver 4.2 allows remote attackers to execute arbitrary
CVE-2000-0318 HIGH 7.5 DOWNGRADE Atrium Mercur Mail Server 3.2 allows local attackers to read other user's email and create arbitrary files via
CVE-2000-0239 MEDIUM 5.0 DOWNGRADE DOWNGRADE Buffer overflow in the MERCUR WebView WebMail server allows remote attackers to cause a denial of service via
CVE-2000-0198 MEDIUM 5.0 DOWNGRADE DOWNGRADE Buffer overflow in POP3 and IMAP servers in the MERCUR mail server suite allows remote attackers to cause a de

References

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