NVD / CVE Program· CNA redhat

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, whic

Noroxi assessment

Priority: Monitor (action score 21/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 3.2% (FIRST EPSS); higher than 88.1% of all records.
No special conditions are required; it is repeatable.
Fixed version: ntp (Debian:11) 1:4.2.4p4+dfsg-8; ntp (Debian:4.0) 1:4.2.2.p4+dfsg-2etch1; ntp (Red Hat:enterprise_linux:4::as) 0:4.2.0.a.20040617-8.el4_7.1.

Low priority for now. Upgrade to ntp (Debian:11) 1:4.2.4p4+dfsg-8; ntp (Debian:4.0) 1:4.2.2.p4+dfsg-2etch1; ntp (Red Hat:enterprise_linux:4::as) 0:4.2.0.a.20040617-8.el4_7.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.0 · v2.0—No exploit Fix available

Published: Jan 7, 2009
Updated: Jun 16, 2026
EPSS: 3.2% · 88th percentile
CWE: CWE-287

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 20 / 40 · 5.0 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 3.2%

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No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
ntp	ntp	cpe:2.3:a:ntp:ntp

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

ntp ntpup to 4.2.4p4 inclusive
ntp ntp4.2.0
ntp ntp4.2.2
ntp ntp4.2.4p1
ntp ntp4.2.4p2
ntp ntp4.2.4p3

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:11	ntp	before 1:4.2.4p4+dfsg-8	1:4.2.4p4+dfsg-8
Debian:4.0	ntp	before 1:4.2.2.p4+dfsg-2etch1	1:4.2.2.p4+dfsg-2etch1
Red Hat:enterprise_linux:4::as	ntp	before 0:4.2.0.a.20040617-8.el4_7.1	0:4.2.0.a.20040617-8.el4_7.1
Red Hat:enterprise_linux:4::as	ntp-debuginfo	before 0:4.2.0.a.20040617-8.el4_7.1	0:4.2.0.a.20040617-8.el4_7.1
Red Hat:enterprise_linux:5::client	ntp	before 0:4.2.2p1-9.el5_3.1	0:4.2.2p1-9.el5_3.1
Red Hat:enterprise_linux:5::client	ntp-debuginfo	before 0:4.2.2p1-9.el5_3.1	0:4.2.2p1-9.el5_3.1

Same product

ntp: all records

Other highest-scoring records for the same primary product.

CVE-2015-7871Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.
64This week
CVE-2014-9295Multiple stack-based buffer overflows in ntpd in NTP before 4.2.8 allow remote attackers to execute arbitrary code via a crafted packet, rel
54Plan
CVE-2013-5211The monlist feature in ntp_request.c in ntpd in NTP before 4.2.7p26 allows remote attackers to cause a denial of service (traffic amplificat
49Plan

Published before and after this one in the same product

← EarlierCVE-2004-0657Aug 6, 2004 · Integer overflow in the NTP daemon (NTPd) before 4.0 causes the NTP server to return the wrong date/time offset when a client requests a dat
21Monitor
Later →CVE-2009-0159Apr 14, 2009 · Stack-based buffer overflow in the cookedprint function in ntpq/ntpq.c in ntpq in NTP before 4.2.4p7-RC2 allows remote NTP servers to execut
31Monitor
Later →CVE-2009-1252May 19, 2009 · Stack-based buffer overflow in the crypto_recv function in ntp_crypto.c in ntpd in NTP before 4.2.4p7 and 4.2.5 before 4.2.5p74, when OpenSS
33Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
debian:ntp	1:4.2.4p4+dfsg-8 · Debian:11	Package registry (OSV)
red hat:ntp	0:4.2.0.a.20040617-8.el4_7.1 · Red Hat:enterprise_linux:4::as	Package registry (OSV)
red hat:ntp-debuginfo	0:4.2.0.a.20040617-8.el4_7.1 · Red Hat:enterprise_linux:4::as	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

No special conditions are required; it is repeatable.

If successful

Confidentiality: P · data can be read
Integrity: none
Availability: none

Attack complexity: Low
Confidentiality impact: P
Integrity impact: None
Availability impact: None

Weakness class (CWE)

CWE-287 · Improper Authentication

CVSS vector

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

nvd-primary

Root cause

Authentication is added route by route instead of being enforced in one place. When a route added later bypasses the shared middleware, the session check never runs for it.

The bug in code

The whole CWE-287 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1app.use("/admin", requireSession, adminRouter);
2

3// Route added later skips the middleware
4app.post("/admin-api/config", updateConfig);

Fixed

1const admin = express.Router();
2admin.use(requireSession, requireRole("admin"));
3

4admin.post("/config", updateConfig);
5app.use("/admin", admin);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Change log

Fix✗ → ✓Sep 28, 2026, 10:44 PM UTC

For records you follow, these changes also arrive as notifications. →

References

lists.apple.com/archives/security-announce/2009/May/msg00002.html

Show all references (18 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records