How severe is CVE-2009-4171?

CVE-2009-4171 has a CVSS 2.0 base score of 4.3, rated medium severity.

Is CVE-2009-4171 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (91st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-4171?

CVE-2009-4171 affects Yahoo Messenger. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2009-4171?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2009-4171 published?

CVE-2009-4171 was published on 2009-12-02 and last updated on 2026-06-16.

CVE-2009-4171

CVE-2009-4171 is a medium-severity vulnerability in Yahoo Messenger with a CVSS 2.0 base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-119.

Key facts

Severity: Medium (CVSS 2.0 base score 4.3)
EPSS exploit prediction: 5% (91st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-119
Affected product: Yahoo Messenger
Published: 2009-12-02
Last modified: 2026-06-16

Description

An ActiveX control in YahooBridgeLib.dll for Yahoo! Messenger 9.0.0.2162, and possibly other 9.0 versions, allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) by calling the RegisterMe method with a long argument.

Frequently asked questions

What is CVE-2009-4171?: An ActiveX control in YahooBridgeLib.dll for Yahoo! Messenger 9.0.0.2162, and possibly other 9.0 versions, allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) by calling the RegisterMe method with a long argument.
How severe is CVE-2009-4171?: CVE-2009-4171 has a CVSS 2.0 base score of 4.3, rated medium severity.
Is CVE-2009-4171 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (91st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-4171?: CVE-2009-4171 affects Yahoo Messenger. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2009-4171?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-4171 published?: CVE-2009-4171 was published on 2009-12-02 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:yahoo:messenger:9.0.0.2162:*:*:*:*:*:*:*

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