CVE-2005-2403: The login protocol in RealChat 3.5.1b does not use authentication, which allows remote attackers to log on as

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MEDIUM 5.0DOWNGRADE

CVE-2005-2403 is a medium-severity flaw (CVSS 5.0) affecting realchat. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The login protocol in RealChat 3.5.1b does not use authentication, which allows remote attackers to log on as other users by sniffing the beginning of a chat session and replaying it via a modified username.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	1.5% (top 26%)
CISA exploited list	No
Published	2005-07-27
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: realchat

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

Am I affected?

Timeline

2005-07-27 04:00 UTCPublished CVE record published
2026-06-16 22:14 UTCUpdated Record last modified

realchat realchat DOWNGRADE

Affected: 3.5.1b

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.5.1b

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.5.1b (Debian / Ubuntu)

apt-cache madison realchat sudo apt install realchat=<VERSION_BEFORE_3.5.1b> sudo apt-mark hold realchat

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

dnf --showduplicates list realchat sudo dnf downgrade realchat-<VERSION_BEFORE_3.5.1b> sudo dnf versionlock add realchat

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-2005-2403?

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

Is CVE-2005-2403 being exploited?

CVE-2005-2403 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-2005-2403 affect?

CVE-2005-2403 affects realchat. Severity is medium (CVSS 5.0). The login protocol in RealChat 3.5.1b does not use authentication, which allows remote attackers to log on as other users by sniffing the beginning of a chat session and replaying it via a modified username.

How urgent is CVE-2005-2403?

Priority 41/100. Public exploit reference

References

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