CVE-2020-12883 Information

Description

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.

CVSS Vector

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

Reference

https://github.com/ARMmbed/mbed-coap/pull/116 https://github.com/ARMmbed/mbed-os/issues/12925 https://github.com/ARMmbed/mbed-os/issues/12926 https://github.com/ARMmbed/mbed-os/issues/12927

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

NONE

Base Score

HIGH

Base Severity

9.1