CVE-2009-0021
CWE-287Published: January 7, 2009· Updated: Jun 16, 2026
Official 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.
Technical Analysis
CVE-2009-0021 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
From a weakness classification perspective (CWE-287): Authentication bypass vulnerabilities allow attackers to access protected resources without valid credentials.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (38)
Quick Facts
Related CVEs (CWE-287)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2009-0021 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts