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Net::Server's log() Function Syslog Usage Allows for a Format String
Vulnerability
------------------------------------------------------------------------
SUMMARY
The undocumented but frequently used "log" function provided by the
Net::Server Perl module is not safe against format string vulnerability.
DETAILS
Vulnerable Systems:
* Net::Server version 0.87
The syslog call in function log is implemented like following:
### log only to syslog if setup to do syslog
if( $prop->{log_file} eq 'Sys::Syslog' ){
$level = $level!~/^\d+$/ ? $level : $Net::Server::syslog_map->{$level}
;
Sys::Syslog::syslog($level,@_); <---!!!!!!
return;
}
Sys::Syslog tells how to use function "syslog":
syslog $priority, $format, @args
If $priority permits, logs ($format, @args) printed as by
"printf(3V)", with the addition that %m is replaced with "$!"
(the latest error message).
Unfortunately, the function "log" of Net::Server put now the first given
log argument into "syslog" function as format string, and the others as
arguments.
Workaround:
As a workaround, programs using "log" of Net::Server can replace a single
"%" by "%%", but only in case of when syslog is used.
Impact of workaround: programs which call "log" of Net::Server with format
string in first log argument will break.
ADDITIONAL INFORMATION
The information has been provided by <mailto:pbieringer@aerasec.de> Dr.
Peter Bieringer.
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