The advisory could be found here: http://securenetwork.it/ricerca/advisory/download/SN-2008-02.txt Secure Network - Security Research Advisory Vuln name: Ruby rb_ary_fill() DOS Systems affected: ruby 1.8.x, 1.9.x Systems not affected: - Severity: Medium Local/Remote: Local/Remote Vendor URL: http://www.ruby-lang.org/ Author(s): Vincenzo "snagg" Iozzo - snagg@xxxxxxxxxxxxxxxx Vendor disclosure: 23rd June 2008 Vendor acknowledged: 25th June 2008 Vendor patch release: 25th June 2008 Public disclosure: 30th June 2008 Advisory number: SN-2008-02 Advisory URL: http://www.securenetwork.it/advisories/ *** SUMMARY *** Ruby is an interpreted language, used in a wide range of applications. The specific issue is a Denial of Services vulnerability, caused by an integer overflow. However it doesn't allow arbitrary code execution. On Ruby on Rails, an attacker may craft specific requests and by XSS (for example) can cause a legitimate user to crash the web server. *** VULNERABILITY DETAILS *** Integer overflow (Dos). The vulnerability was found in rb_ary_fill(). Looking inside the application source code: ###### CUT HERE ###### rb_ary_modify(ary); end = beg + len; if (end < 0) { rb_raise(rb_eArgError, "argument too big"); } if (end > RARRAY(ary)->len) { if (end >= RARRAY(ary)->aux.capa) { REALLOC_N(RARRAY(ary)->ptr, VALUE, end); RARRAY(ary)->aux.capa = end; } ###### CUT HERE ###### The len value is incremented by one in a previous function and it is specified by the user. The lack of sanity check on the input, leads to an integer overflow here: ###### CUT HERE ###### REALLOC_N(RARRAY(ary)->ptr, VALUE, end); ###### CUT HERE ###### This macro, in fact, will allocate end * VALUE. On 32bit architectures VALUE is 4. If an attacker specifies a value of 0x3fffffff, this macro will allocate a memory region of 0, so that next time ary->ptr is accessed, it will raise a SIGSEGV.(NULL referencing) *** EXPLOIT *** a = [] a.fill("A",0..0x3fffffff) *** FIX INFORMATION *** http://svn.ruby-lang.org/cgi-bin/viewvc.cgi/trunk/array.c?view=markup ********************* *** LEGAL NOTICES *** ********************* Secure Network (www.securenetwork.it) is an information security company, which provides consulting and training services, and engages in security research and development. We are committed to open, full disclosure of vulnerabilities, cooperating with software developers for properly handling disclosure issues. This advisory is copyright 2008 Secure Network S.r.l. Permission is hereby granted for the redistribution of this alert, provided that it is not altered except by reformatting it, and that due credit is given. It may not be edited in any way without the express consent of Secure Network S.r.l. Permission is explicitly given for insertion in vulnerability databases and similars, provided that due credit is given to Secure Network The information in the advisory is believed to be accurate at the time of publishing based on currently available information. This information is provided as-is, as a free service to the community by Secure Network research staff. There are no warranties with regard to this information. Secure Network does not accept any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information. If you have any comments or inquiries, or any issue with what is reported in this advisory, please inform us as soon as possible. E-mail: securenetwork@xxxxxxxxxxxxxxxx GPG/PGP key: http://www.securenetwork.it/pgpkeys/Secure%20Network.asc Phone: +39 02 24126788
