CVE-2020-12883: 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 fun...

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.

Metrics

CVSS 3.1

9.1/10

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

EPSS Probability

1.78%

75.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-125

Affected Software

Vendor	Product	Versions
Arm	Mbed Os	5.15.3

References

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

Timeline

Published: Jun 18, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-12883?

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.

How severe is CVE-2020-12883?

CVE-2020-12883 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 1.78% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12883?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.