Debian LinuxOperating system · Debian
CVE-2013-6890
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · unediteddenyhosts 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceDenyhosts 2.6 contains an incorrect regular expression in its authentication log parsing logic. When processing log entries, this flawed regex misinterprets specially crafted login names, causing the tool to incorrectly identify and block legitimate IP addresses. This results in a denial of service condition where valid users are prevented from accessing the system.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Debian LinuxOperating system
= 6.0= 7.0= 7.1
FedoraOperating system
all versions= 2.6CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Confirm Denyhosts is installedRun 'denyhosts --version' or check your package manager for denyhosts (e.g., dpkg -l denyhosts, rpm -qa denyhosts)Affected if Denyhosts is installed and the version displayed is 2.6
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Check if Denyhosts daemon is activeCheck the running processes for denyhosts or check service status (e.g., service denyhosts status, systemctl status denyhosts)Affected if Denyhosts daemon is actively running and processing logs
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Verify Denyhosts is configured to parse authentication logsExamine the Denyhosts configuration file (typically denyhosts.conf) and confirm the path to your system authentication log (such as /var/log/auth.log or /var/log/secure) is properly specified under the SECURE_LOG directiveAffected if Denyhosts is configured with a valid authentication log path for parsing
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Compare installed version to affected rangesMatch your confirmed Denyhosts version (should be 2.6 for this CVE) against the affected versions: Denyhosts 2.6, Debian 6.0/7.0/7.1 with Denyhosts 2.6, or Fedora all versions with Denyhosts 2.6Affected if The installed Denyhosts version is exactly 2.6 and it is actively parsing logs
You are affected if Denyhosts version 2.6 is installed and actively running with authentication log parsing enabled, as the flawed regex in this version can misidentify legitimate login attempts and block valid IP addresses.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to a patched version of denyhosts that contains the corrected regular expression, or manually review and fix the regex pattern used in the log parsing module to properly handle edge-case login names.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing4.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2013-6890 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2013-6890 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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