Libming 0.4.8 Denial Of Service

Libming version 0.4.8 suffers from a denial of service vulnerability.


MD5 | 4244de5a4d322510400905914ca3db5b



[CVE-2017-8782]Libming readString denial of service
================
CVE ID : CVE-2017-8782
Author : qflb.wu
===============




Introduction:
=============
Ming is a Flash (SWF) output library. It can be used from PHP, Perl, Ruby, Python, C, C++, Java, and probably more on the way.


Affected version:
=====
0.4.8


Vulnerability Description:
==========================
the readString function in util/read.c and util/old/read.c in libming 0.4.8 can cause a denial of service via a large file via listswf listaction etc


char *readString(FILE *f)
{
int len = 0, buflen = 256;
char c, *buf, *p;


buf = (char *)malloc(sizeof(char)*256);
p = buf;


while((c=(char)readUInt8(f)) != '\0')
{
if(len >= buflen-2)
{
buf = (char *)realloc(buf, sizeof(char)*(buflen+256)); <=========
buflen += 256;
p = buf+len;
}


switch(c)
{
case '\n':
*(p++) = '\\';*(p++) = 'n';++len;break;
case '\t':
*(p++) = '\\';*(p++) = 't';++len;break;
case '\r':
*(p++) = '\\';*(p++) = 'r';++len;break;
default:
*(p++) = c;
}


++len;
}


*p = 0;


return buf;
}


the source code has not check the return of the realloc function ,
if the crafted file is large enough , realloc may cause memory allocation error
or
buflen+256 may result in Integer Overflow and buflen+256 may become zero , realloc(buf,0) --> free.
==========================




qflb.wu () dbappsecurity com cn




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