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Buffer overflows were discovered in the CoAP library in Arm Mbed OS 5.14.0. The CoAP parser is responsible for parsing received CoAP packets. The function sn_coap_parser_options_parse() parses CoAP input linearly using a while loop. Once an option is parsed in a loop, the current point (*packet_data_pptr) is increased correspondingly. The pointer is restricted by the size of the received buffer, as well as by the 0xFF delimiter byte. Inside each while loop, the check of the value of *packet_data_pptr is not strictly enforced. More specifically, inside a loop, *packet_data_pptr could be increased and then dereferenced without checking. Moreover, there are many other functions in the format of sn_coap_parser_****() that do not check whether the pointer is within the bounds of the allocated buffer. All of these lead to heap-based or stack-based buffer overflows, depending on how the CoAP packet buffer is allocated.

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ARM Mbed OS CoAP library 缓冲区错误漏洞

ARM Mbed OS是英国ARM公司的一套专用于物联网的开源嵌入式操作系统。CoAP library是其中的一个约束应用协议（CoAP）库。 Arm Mbed OS 5.14.0版本中的CoAP library的‘sn_coap_parser_options_parse’函数存在缓冲区错误漏洞，该漏洞源于程序没有正确检查边界。远程攻击者可借助特制文件利用该漏洞在系统上执行任意代码。

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