CVE-2020-12887

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Memory leaks were discovered in the CoAP library in Arm Mbed OS 5.15.3 when using the Arm mbed-coap library 5.1.5. The CoAP parser is responsible for parsing received CoAP packets. The function sn_coap_parser_options_parse() parses the CoAP option number field of all options present in the input packet. Each option number is calculated as a sum of the previous option number and a delta of the current option. The delta and the previous option number are expressed as unsigned 16-bit integers. Due to lack of overflow detection, it is possible to craft a packet that wraps the option number around and results in the same option number being processed again in a single packet. Certain options allocate memory by calling a memory allocation function. In the cases of COAP_OPTION_URI_QUERY, COAP_OPTION_URI_PATH, COAP_OPTION_LOCATION_QUERY, and COAP_OPTION_ETAG, there is no check on whether memory has already been allocated, which in conjunction with the option number integer overflow may lead to multiple assignments of allocated memory to a single pointer. This has been demonstrated to lead to memory leak by buffer orphaning. As a result, the memory is never freed.

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ARM Mbed OS CoAP library 输入验证错误漏洞

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 5.15.3版本中的CoAP library存在输入验证错误漏洞。攻击者可利用该漏洞造成拒绝服务（内存泄露）。

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