Skip to content
Fencer Vulns
critical 9.1

CVE-2020-12883 json

Buffer over-reads were discovered in the CoAP library in Arm Mbed OS 5.15.3.

published 2020-06-18 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-5164

cvss
9.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.8%
EPSS 1.8% chance of exploitation in 30 days, percentile 78%
public exploits
0
none known

Summary

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.

Patch / fix

Exploit prediction

1.78% chance of exploitation in the next 30 days, higher than 78% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
NVD 2.0 6.4 AV:N/AC:L/Au:N/C:P/I:N/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.