Chargen UDP Service Remote DoS

medium Nessus Plugin ID 10043
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VPR Score: 3.6


The remote host is running a 'chargen' service.


When contacted, chargen responds with some random characters (something like all the characters in the alphabet in a row). When contacted via UDP, it will respond with a single UDP packet. When contacted via TCP, it will continue spewing characters until the client closes the connection.

The purpose of this service was to mostly test the TCP/IP protocol by itself, to make sure that all the packets were arriving at their destination unaltered. It is unused these days, so it is suggested you disable it, as an attacker may use it to set up an attack against this host, or against a third-party host using this host as a relay.

An easy attack is 'ping-pong' in which an attacker spoofs a packet between two machines running chargen. This will cause them to spew characters at each other, slowing the machines down and saturating the network.


- Under Unix systems, comment out the 'chargen' line in /etc/inetd.conf and restart the inetd process

- Under Windows systems, set the following registry keys to 0 :
HKLM\System\CurrentControlSet\Services\SimpTCP\Parameters\EnableTcpChargen HKLM\System\CurrentControlSet\Services\SimpTCP\Parameters\EnableUdpChargen

Then launch cmd.exe and type :

net stop simptcp net start simptcp

To restart the service.

See Also

Plugin Details

Severity: Medium

ID: 10043

File Name: chargen.nasl

Version: 1.40

Type: remote

Published: 11/29/1999

Updated: 6/12/2020

Dependencies: find_service1.nasl

Risk Information

Risk Factor: Medium

VPR Score: 3.6

CVSS v2.0

Base Score: 5

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:P

Vulnerability Information

Exploit Available: true

Exploit Ease: Exploits are available

Vulnerability Publication Date: 2/8/1996

Exploitable With

Metasploit (Chargen Probe Utility)

Reference Information

CVE: CVE-1999-0103