CVE-2019-17212: mbed Improper Validation of Array Index

Vulnerability summary

CVE-2019-17212 is a high (CVSS 10.0) Improper Validation of Array Index vulnerability in mbed. EPSS estimates a 3.06% chance of exploitation in the next 30 days, higher than 87.4% of scored vulnerabilities.

Timeline

1. 05-11-2019
   PublishedVulnerability first disclosed.
2. 05-08-2024
   Last modifiedVulnerability information updated.

Description

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.

• CWE-129Improper Validation of Array IndexThe product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.