CVE-2009-4831: Cerulean Studios Trillian 3.1 Basic does not check SSL certificates during MSN authentication, which allows re

Routine

MEDIUM 5.8DOWNGRADE

CVE-2009-4831 is a medium-severity flaw (CVSS 5.8) affecting trillian. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cerulean Studios Trillian 3.1 Basic does not check SSL certificates during MSN authentication, which allows remote attackers to obtain MSN credentials via a man-in-the-middle attack with a spoofed SSL certificate.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	5.8 (Medium)
EPSS exploit chance	1.4% (top 28%)
CISA exploited list	No
Weakness	CWE-295
Published	2010-04-29
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: cerulean studios

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

Am I affected?

Timeline

2010-04-29 19:30 UTCPublished CVE record published
2026-06-16 23:14 UTCUpdated Record last modified

cerulean studios trillian DOWNGRADE

Affected: 3.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.1 (Debian / Ubuntu)

apt-cache madison trillian sudo apt install trillian=<VERSION_BEFORE_3.1> sudo apt-mark hold trillian

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

dnf --showduplicates list trillian sudo dnf downgrade trillian-<VERSION_BEFORE_3.1> sudo dnf versionlock add trillian

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-2009-4831?

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

Is CVE-2009-4831 being exploited?

CVE-2009-4831 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-2009-4831 affect?

CVE-2009-4831 affects trillian. Severity is medium (CVSS 5.8). Cerulean Studios Trillian 3.1 Basic does not check SSL certificates during MSN authentication, which allows remote attackers to obtain MSN credentials via a man-in-the-middle attack with a spoofed SSL certificate.

How urgent is CVE-2009-4831?

Priority 38/100. No elevated risk signals yet.

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References

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