CVE-2019-17212 Information

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.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Reference

https://github.com/ARMmbed/mbed-os/blob/d91ed5fa42ea0f32e4422a3c562e7b045a17da40/features/frameworks/mbed-coap/source/sn_coap_parser.cL257 https://github.com/ARMmbed/mbed-os/blob/d91ed5fa42ea0f32e4422a3c562e7b045a17da40/features/frameworks/mbed-coap/source/sn_coap_parser.cL301 https://github.com/ARMmbed/mbed-os/blob/d91ed5fa42ea0f32e4422a3c562e7b045a17da40/features/frameworks/mbed-coap/source/sn_coap_parser.cL310 https://github.com/ARMmbed/mbed-os/blob/d91ed5fa42ea0f32e4422a3c562e7b045a17da40/features/frameworks/mbed-coap/source/sn_coap_parser.cL313 https://github.com/ARMmbed/mbed-os/blob/d91ed5fa42ea0f32e4422a3c562e7b045a17da40/features/frameworks/mbed-coap/source/sn_coap_parser.cL331 https://github.com/ARMmbed/mbed-os/blob/d91ed5fa42ea0f32e4422a3c562e7b045a17da40/features/frameworks/mbed-coap/source/sn_coap_parser.cL660 https://github.com/ARMmbed/mbed-os/issues/11803

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

9.8