How severe is CVE-2009-3639?

CVE-2009-3639 has a CVSS 2.0 base score of 5.8, rated medium severity.

Is CVE-2009-3639 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-3639?

CVE-2009-3639 primarily affects Proftpd. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-3639?

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

When was CVE-2009-3639 published?

CVE-2009-3639 was published on 2009-10-28 and last updated on 2026-06-16.

CVE-2009-3639

CVE-2009-3639 is a medium-severity vulnerability in Proftpd with a CVSS 2.0 base score of 5.8. 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-310.

Key facts

Severity: Medium (CVSS 2.0 base score 5.8)
EPSS exploit prediction: 6% (92nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-310
Affected product: Proftpd
Published: 2009-10-28
Last modified: 2026-06-16

Description

The mod_tls module in ProFTPD before 1.3.2b, and 1.3.3 before 1.3.3rc2, when the dNSNameRequired TLS option is enabled, does not properly handle a '\0' character in a domain name in the Subject Alternative Name field of an X.509 client certificate, which allows remote attackers to bypass intended client-hostname restrictions via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.

Frequently asked questions

What is CVE-2009-3639?: The mod_tls module in ProFTPD before 1.3.2b, and 1.3.3 before 1.3.3rc2, when the dNSNameRequired TLS option is enabled, does not properly handle a '\0' character in a domain name in the Subject Alternative Name field of an X.509 client certificate, which allows remote attackers to bypass intended client-hostname restrictions via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
How severe is CVE-2009-3639?: CVE-2009-3639 has a CVSS 2.0 base score of 5.8, rated medium severity.
Is CVE-2009-3639 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-3639?: CVE-2009-3639 primarily affects Proftpd. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-3639?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-3639 published?: CVE-2009-3639 was published on 2009-10-28 and last updated on 2026-06-16.

References

Affected products (7)

cpe:2.3:a:proftpd:proftpd:*:a:*:*:*:*:*:*
cpe:2.3:a:proftpd:proftpd:1.3.1:*:*:*:*:*:*:*
cpe:2.3:a:proftpd:proftpd:1.3.2:*:*:*:*:*:*:*
cpe:2.3:a:proftpd:proftpd:1.3.2:rc1:*:*:*:*:*:*
cpe:2.3:a:proftpd:proftpd:1.3.2:rc2:*:*:*:*:*:*
cpe:2.3:a:proftpd:proftpd:1.3.2:rc4:*:*:*:*:*:*
cpe:2.3:a:proftpd:proftpd:1.3.3:rc1:*:*:*:*:*:*

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