CVE-2004-0777: Format string vulnerability in the auth_debug function in Courier-IMAP 1.6.0 through 2.2.1 and 3.x through 3.0

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HIGH 7.5DOWNGRADE

CVE-2004-0777 is a high-severity flaw (CVSS 7.5) affecting courier-imap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Format string vulnerability in the auth_debug function in Courier-IMAP 1.6.0 through 2.2.1 and 3.x through 3.0.3, when login debugging (DEBUG_LOGIN) is enabled, allows remote attackers to execute arbitrary code.

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	10.9% (top 4%)
CISA exploited list	No
Weakness	CWE-134
Published	2004-10-20
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: inter7

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

Am I affected?

Timeline

2004-10-20 04:00 UTCPublished CVE record published
2026-06-16 22:06 UTCUpdated Record last modified

inter7 courier-imap DOWNGRADE

Affected: 1.6 · 1.7 · 2.0.0 · 2.1 · 2.1.1 · 2.1.2 · 2.2.0 · 2.2.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.6

1. Check installed version

apt-cache policy courier-imap || rpm -q courier-imap || courier-imap --version

2. No fixed release: DOWNGRADE to a release before 1.6 (Debian / Ubuntu)

apt-cache madison courier-imap sudo apt install courier-imap=<VERSION_BEFORE_1.6> sudo apt-mark hold courier-imap

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

dnf --showduplicates list courier-imap sudo dnf downgrade courier-imap-<VERSION_BEFORE_1.6> sudo dnf versionlock add courier-imap

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: Courier-IMAP 3.0.2-r1 - 'auth_debug()' Remote Format String

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-2004-0777?

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

Is CVE-2004-0777 being exploited?

CVE-2004-0777 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-2004-0777 affect?

CVE-2004-0777 affects courier-imap. Severity is high (CVSS 7.5). Format string vulnerability in the auth_debug function in Courier-IMAP 1.6.0 through 2.2.1 and 3.x through 3.0.3, when login debugging (DEBUG_LOGIN) is enabled, allows remote attackers to execute arbitrary code.

How urgent is CVE-2004-0777?

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

Related CVEs

CVE-2007-2173 HIGH 10.0 DOWNGRADE Eval injection vulnerability in (1) courier-imapd.indirect and (2) courier-pop3d.indirect in Courier-IMAP befo
CVE-2004-0224 HIGH 7.5 DOWNGRADE DOWNGRADE Multiple buffer overflows in (1) iso2022jp.c or (2) shiftjis.c for Courier-IMAP before 3.0.0, Courier before 0
CVE-2003-0040 HIGH 7.5 DOWNGRADE DOWNGRADE SQL injection vulnerability in the PostgreSQL auth module for courier 0.40 and earlier allows remote attackers

References

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