High 7.5Published Oct 9, 2026

CVE-2026-107838RIOT: nanocoap_fileserver ignores response initialization failure, leading to reachable assertion

Updated under an hour ago (2026-10-19 07:30 UTC)

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It affects RIOT-OS RIOT. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.34%, higher than 26% of scored CVEs.

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Every CVE for RIOT-OS RIOT

Exploited in the last 30 days

RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. From version 2023.07 through version 2026.07, nanocoap_fileserver callers in sys/net/application_layer/nanocoap/fileserver.c ignore a failure returned by _resp_init() when coap_build_reply() cannot fit a response header into the response buffer. A remote client can send a CoAP request with a sufficiently large extended token when nanocoap_token_ext is enabled, causing response initialization to fail while _get_file() or _get_directory() continues with stale response state. The path then reaches _calc_szx2() and its pdu->payload_len > reserve assertion, terminating the affected service or device task. No fixed release is available as of this review.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-252, CWE-617
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.34% (percentile 26)
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Oct 13, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

RIOT-OS RIOT riot_os:riot (from the name)	from 2023.07, <= 2026.07	CNA record

References

https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-39j3-3v73-5mj2x-refsource-confirm
https://github.com/RIOT-OS/RIOT/pull/22745x-refsource-misc
https://github.com/RIOT-OS/RIOT/commit/d3a47289c58d108575a19e623e4d3f647659e743x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.