CVE-2013-6890 Denial of service in n/a

What is CVE-2013-6890?

CVE-2013-6890 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 23 Dec 2013. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

denyhosts 2.6 uses an incorrect regular expression when analyzing authentication logs, which allows remote attackers to cause a denial of service (incorrect block of IP addresses) via crafted login names.

Weakness: CWE-287

Which versions are affected by CVE-2013-6890?

It affects 3 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Phil Schwartz Denyhosts.

How do I fix CVE-2013-6890?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2013-6890 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2013-6890 exists.

Public exploit code: 1 Exploit-DB entry.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DSA-2826-1, GHSA-f4g4-953x-f5pm, MGASA-2014-0080.