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CVE-2009-0021

16
FAUCET Score

CVE-2009-0021 describes a vulnerability in NTP versions 4.2.4 before 4.2.4p5 and 4.2.5 before 4.2.5p150. It allows remote attackers to bypass certificate chain validation by exploiting improper handling of the OpenSSL EVP_VerifyFinal function's return value, specifically with malformed SSL/TLS signatures for DSA and ECDSA keys. This vulnerability has a CVSS score of 5.0 (Medium), indicating a network-based attack with low complexity, requiring no authentication, and potentially leading to partial confidentiality impact. There is no known impact on integrity or availability. Currently, there is no evidence of active exploitation, public exploit code (e.g., Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 4.2.4p4CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:*:*:*:*:*:*:*:*
4.2.0CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.2.0:*:*:*:*:*:*:*
4.2.2CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.2.2:*:*:*:*:*:*:*
4.2.4p1CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.2.4p1:*:*:*:*:*:*:*
4.2.4p2CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.2.4p2:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

5.0MEDIUM

AV:N/AC:L/Au:N/C:P/I:N/A:N

Confidentiality Impact
PARTIAL
Integrity Impact
NONE
Availability Impact
NONE
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Exploitability Score
10.0
Impact Score
2.9
CvssVersion
2.0

Exploit Intelligence

EPSS Score
3.10%
Probability of exploitation in next 30 days
EPSS Percentile
86.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0310 is in the 81st percentile among its peer group of 23,723 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 4Fixed in: ntp-0:4.2.0.a.20040617-8.el4_7.1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: ntp-0:4.2.2p1-9.el5_3.1
View patch

Vendor Advisories (1)

redhatCVE-2009-0021Moderate

ntp incorrectly checks for malformed signatures

Jan 7, 2009

References

lists.apple.com / archives/security-announce/2009/May/msg00002.html
lists.opensuse.org / opensuse-security-announce/2009-03/msg00000.html
lists.opensuse.org / opensuse-security-announce/2009-04/msg00003.html
secunia.com / advisories/33406
Vendor Advisory
secunia.com / advisories/33558
Vendor Advisory
secunia.com / advisories/33648
Vendor Advisory
secunia.com / advisories/34642
Vendor Advisory
secunia.com / advisories/35074
Vendor Advisory
slackware.com / security/viewer.php
lists.ntp.org / pipermail/announce/2009-January/000055.html
oval.cisecurity.org / repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10035
support.apple.com / kb/HT3549
ocert.org / advisories/ocert-2008-016.html
redhat.com / support/errata/RHSA-2009-0046.html
securityfocus.com / archive/1/499827/100/0/threaded
securitytracker.com / id
us-cert.gov / cas/techalerts/TA09-133A.html
US Government Resource
vupen.com / english/advisories/2009/0042
Vendor Advisory
vupen.com / english/advisories/2009/1297
Vendor Advisory