How severe is CVE-2009-0021?

CVE-2009-0021 has a CVSS 2.0 base score of 5.0, rated medium severity.

Is CVE-2009-0021 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-0021?

CVE-2009-0021 primarily affects Ntp. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-0021?

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

When was CVE-2009-0021 published?

CVE-2009-0021 was published on 2009-01-07 and last updated on 2026-06-16.

CVE-2009-0021

CVE-2009-0021 is a medium-severity vulnerability in Ntp with a CVSS 2.0 base score of 5.0. 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-287.

Key facts

Severity: Medium (CVSS 2.0 base score 5.0)
EPSS exploit prediction: 3% (87th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Ntp
Published: 2009-01-07
Last modified: 2026-06-16

Description

NTP 4.2.4 before 4.2.4p5 and 4.2.5 before 4.2.5p150 does not properly check the return value from the OpenSSL EVP_VerifyFinal function, which allows remote attackers to bypass validation of the certificate chain via a malformed SSL/TLS signature for DSA and ECDSA keys, a similar vulnerability to CVE-2008-5077.

Frequently asked questions

What is CVE-2009-0021?: NTP 4.2.4 before 4.2.4p5 and 4.2.5 before 4.2.5p150 does not properly check the return value from the OpenSSL EVP_VerifyFinal function, which allows remote attackers to bypass validation of the certificate chain via a malformed SSL/TLS signature for DSA and ECDSA keys, a similar vulnerability to CVE-2008-5077.
How severe is CVE-2009-0021?: CVE-2009-0021 has a CVSS 2.0 base score of 5.0, rated medium severity.
Is CVE-2009-0021 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-0021?: CVE-2009-0021 primarily affects Ntp. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-0021?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-0021 published?: CVE-2009-0021 was published on 2009-01-07 and last updated on 2026-06-16.

References

Affected products (6)

cpe:2.3:a:ntp:ntp:*:*:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.0:*:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.2:*:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.4p1:*:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.4p2:*:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.4p3:*:*:*:*:*:*:*

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Other CWE-287 (Improper Authentication) vulnerabilities

CVE-2026-45480 — Critical (CVSS 10.0): Improper authentication in Azure Active Directory allows an unauthorized attacker to elevate privileges over a network.
CVE-2026-46389 — Critical (CVSS 10.0): UDS Identity Config builds the Keycloak configuration image (realm, plugins, theme, truststore, JARs) consumed by UDS…
CVE-2026-10611 — Critical (CVSS 10.0): An authentication bypass vulnerability exists in MISP when LDAP mixed authentication is enabled with OTP enforcement.…
CVE-2026-47280 — Critical (CVSS 10.0): Improper authentication in Azure Resource Manager (ARM) allows an unauthorized attacker to elevate privileges over a…
CVE-2026-42822 — Critical (CVSS 10.0): Improper authentication in Azure Local Disconnected Operations allows an unauthorized attacker to elevate privileges…
CVE-2026-20182 — Critical (CVSS 10.0): May 2026: This security advisory provides the details and fix information for a vulnerability that was discovered and…

Browse all CWE-287 (Improper Authentication) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

42.200.60.186 (ipv4-addr)
223.197.153.135 (ipv4-addr)