Answer in brief
CVE-2026-107836 records a High severity (CVSS 7.1) vulnerability in RIOT: nanoCoAP Block2 client slice handling underflows on inconsistent server-controlled block size. The current sources do not mark it as known exploited. The current feed maps RIOT-OS/RIOT (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps RIOT-OS/RIOT (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| RIOT-OS/RIOTgeneric | <=2026.07 | = 2026.07 |
Published upstream
Oct 9, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 9, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 9, 2026
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.
Quoted source text, attributed separately from HOL analysis.