CVE-2007-4321

CVE-2007-4321 is a medium-severity vulnerability in Fail2ban with a CVSS 2.0 base score of 6.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Description

fail2ban 0.8 and earlier does not properly parse sshd log files, which allows remote attackers to add arbitrary hosts to the /etc/hosts.deny file and cause a denial of service by adding arbitrary IP addresses to the sshd log file, as demonstrated by logging in via ssh with a client protocol version identification containing an IP address string, a different vector than CVE-2006-6302.

Frequently asked questions

What is CVE-2007-4321?
fail2ban 0.8 and earlier does not properly parse sshd log files, which allows remote attackers to add arbitrary hosts to the /etc/hosts.deny file and cause a denial of service by adding arbitrary IP addresses to the sshd log file, as demonstrated by logging in via ssh with a client protocol version identification containing an IP address string, a different vector than CVE-2006-6302.
How severe is CVE-2007-4321?
CVE-2007-4321 has a CVSS 2.0 base score of 6.8, rated medium severity.
Is CVE-2007-4321 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-2007-4321?
CVE-2007-4321 affects Fail2ban. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2007-4321?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2007-4321 published?
CVE-2007-4321 was published on 2007-08-14 and last updated on 2026-06-16.

References

Affected products (1)

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