CVE-2026-107836: CWE-125: Out-of-bounds Read in RIOT-OS RIOT
Description
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.
CVSS v4.0
Score 7.1high
Affected software
RIOT-OS
RIOT
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
RIOT-OS versions 2026.07 and earlier contain an out-of-bounds read vulnerability in the nanoCoAP client function nanocoap_sock_get_slice() located in sys/net/application_layer/nanocoap/sock.c. The function _block_cb() accepts a Block2 response if the expected block number matches but does not verify that the server-controlled szx and derived offset correspond to the requested block geometry. A malicious CoAP server can exploit this by returning a larger block size with the expected block number, causing an offset underflow in _2buf_slice(). This leads to reading memory before the payload buffer, potentially crashing the client and exposing adjacent memory.
Potential Impact
Exploitation of this vulnerability can cause denial of service due to client crashes and may expose adjacent memory contents, which could lead to information disclosure. The vulnerability does not require privileges or user interaction beyond sending a malicious CoAP response. There are no known exploits in the wild as of the publication date.
Mitigation Recommendations
No fixed release or official patch is currently available for this vulnerability. Users should monitor the vendor advisory for updates and consider applying any future patches once released. Until then, caution is advised when interacting with untrusted CoAP servers.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-10-08T22:34:49.289Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ac92c962cdf04f65675296c
Added to database: 10/09/2026, 18:04:06 UTC
Last enriched: 10/09/2026, 18:18:16 UTC
Last updated: 10/09/2026, 18:57:31 UTC
Views: 15
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