CVE-2020-12883

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Buffer over-reads were discovered in the CoAP library in Arm Mbed OS 5.15.3. 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 option delta and option length bytes. The actual input packet length is not verified against the number of bytes read when processing the option extended delta and the option extended length. Moreover, the calculation of the message_left variable, in the case of non-extended option deltas, is incorrect and indicates more data left for processing than provided in the function input. All of these lead to heap-based or stack-based memory location read access that is outside of the intended boundary of the buffer. Depending on the platform-specific memory management mechanisms, it can lead to processing of unintended inputs or system memory access violation errors.

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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 5.15.3版本中的CoAP library存在缓冲区错误漏洞。攻击者可利用该漏洞造成拒绝服务。

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