CVE-2013-6890

Debian Linux - Authentication Bypass

Title source: rule
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2013-6890. PoCs published by Helmut Grohne.

AI-analyzed exploit summary This exploit leverages a vulnerability in DenyHosts where a specially crafted SSH login attempt can trigger a denial-of-service by causing arbitrary IP addresses to be blocked. The PoC demonstrates this by using an invalid username formatted to manipulate DenyHosts' parsing logic.

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.

Exploits (1)

exploitdb WORKING POC VERIFIED
by Helmut Grohne · textdoslinux
https://www.exploit-db.com/exploits/38909

This exploit leverages a vulnerability in DenyHosts where a specially crafted SSH login attempt can trigger a denial-of-service by causing arbitrary IP addresses to be blocked. The PoC demonstrates this by using an invalid username formatted to manipulate DenyHosts' parsing logic.

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Trivial
Reliability
Reliable
Target: DenyHosts (version not specified)
No auth needed
Prerequisites: SSH access to the target system · DenyHosts installed and active on the target
devstral-2 · analyzed Feb 16, 2026 Full analysis →

References (4)

Core 4
Core References
Vendor Advisory third-party-advisory x_refsource_secunia
http://secunia.com/advisories/56239
Issue Tracking x_refsource_misc
https://bugzilla.redhat.com/show_bug.cgi?id=1045982
Mailing List mailing-list x_refsource_mlist
http://seclists.org/oss-sec/2013/q4/535
Third Party Advisory vendor-advisory x_refsource_debian
http://www.debian.org/security/2013/dsa-2826

Scores

EPSS 0.0890
EPSS Percentile 94.6%

Details

CWE
CWE-287
Status published
Products (5)
debian/debian_linux 6.0
debian/debian_linux 7.0
debian/debian_linux 7.1
fedoraproject/fedora
phil_schwartz/denyhosts 2.6
Published Dec 23, 2013
Tracked Since Feb 18, 2026