RIOT-OS RIOT up to 2026.07 nanoCoAP sock.c nanocoap_sock_get_slice buffer overflow

Summaryinfo

A vulnerability described as critical has been identified in RIOT-OS RIOT up to 2026.07. This issue affects the function nanocoap_sock_get_slice of the file sys/net/application_layer/nanocoap/sock.c of the component nanoCoAP. The manipulation results in buffer overflow. This vulnerability is known as CVE-2026-107836. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability classified as critical has been found in RIOT-OS RIOT up to 2026.07. Affected is the function nanocoap_sock_get_slice of the file sys/net/application_layer/nanocoap/sock.c of the component nanoCoAP. The manipulation with an unknown input leads to a buffer overflow vulnerability. CWE is classifying the issue as CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. In 2026.07 and earlier, the nanoCoAP client function nanocoap_sock_get_slice() in sys/net/application_layer/nanocoap/sock.c accepts a Block2 response when _block_cb() sees the expected block number without also verifying that the server-controlled szx and derived offset match the requested block geometry. A malicious CoAP server can return the expected block number with a larger block size, causing the derived offset to exceed the client slice offset and making ctx->offset - offset underflow in _2buf_slice(). The resulting buffer-relative calculation can read before the payload buffer and crash the client, causing denial of service and potentially exposing adjacent memory. No fixed release is available as of this review.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-107836 since 10/09/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/09/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• RIOT-OS

Name

• RIOT

Version

• 2026.07

Website

• Product: https://github.com/RIOT-OS/RIOT/

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