CVE-2009-3563

CVE-2009-3563 is a medium-severity vulnerability in Ntp with a CVSS 2.0 base score of 6.4. Its EPSS exploit-prediction score of 32% places it in the 98th percentile, indicating an elevated likelihood of exploitation.

Key facts

Description

ntp_request.c in ntpd in NTP before 4.2.4p8, and 4.2.5, allows remote attackers to cause a denial of service (CPU and bandwidth consumption) by using MODE_PRIVATE to send a spoofed (1) request or (2) response packet that triggers a continuous exchange of MODE_PRIVATE error responses between two NTP daemons.

Frequently asked questions

What is CVE-2009-3563?
ntp_request.c in ntpd in NTP before 4.2.4p8, and 4.2.5, allows remote attackers to cause a denial of service (CPU and bandwidth consumption) by using MODE_PRIVATE to send a spoofed (1) request or (2) response packet that triggers a continuous exchange of MODE_PRIVATE error responses between two NTP daemons.
How severe is CVE-2009-3563?
CVE-2009-3563 has a CVSS 2.0 base score of 6.4, rated medium severity.
Is CVE-2009-3563 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 32% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-3563?
CVE-2009-3563 primarily affects Ntp. In total, 21 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-3563?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-3563 published?
CVE-2009-3563 was published on 2009-12-09 and last updated on 2026-06-16.

References

Affected products (21)

More vulnerabilities in Ntp

All CVEs affecting Ntp →

Threat intelligence

Threat-intel indicators referencing this CVE: