Vulnerability CVE-2020-12884


Published: 2020-06-18

Description:
A buffer over-read was 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_multiple_options() parses CoAP options that may occur multiple consecutive times in a single packet. While processing the options, packet_data_pptr is accessed after being incremented by option_len without a prior out-of-bounds memory check. The temp_parsed_uri_query_ptr is validated for a correct range, but the range valid for temp_parsed_uri_query_ptr is derived from the amount of allocated heap memory, not the actual input size. Therefore the check of temp_parsed_uri_query_ptr may be insufficient for safe access to the area pointed to by packet_data_pptr. As a result, access to a memory area outside of the intended boundary of the packet buffer is made.

Type:

CWE-125

(Out-of-bounds Read)

CVSS2 => (AV:N/AC:L/Au:N/C:P/I:N/A:P)

CVSS Base Score
Impact Subscore
Exploitability Subscore
6.4/10
4.9/10
10/10
Exploit range
Attack complexity
Authentication
Remote
Low
No required
Confidentiality impact
Integrity impact
Availability impact
Partial
None
Partial
Affected software
ARM -> Mbed os 

 References:
https://github.com/ARMmbed/mbed-coap/pull/116
https://github.com/ARMmbed/mbed-os/issues/12928

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