Quick answers
- Is CVE-2026-107838 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-107838 being exploited in the wild.
- How severe is CVE-2026-107838?
- High severity, with a CVSS score of 7.5, published 9 October 2026.
- Which products and versions are affected?
- Riot-Os Riot 2023.07 through 2026.07.
- Is there a fix for CVE-2026-107838?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-107838 attacked?
- It is attacked over the network, in an operating system.
- Am I affected by CVE-2026-107838?
- Check whether you run Riot-Os Riot at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The nanocoap_fileserver in sys/net/application_layer/nanocoap/fileserver.c ignores the failure return value from _resp_init() when coap_build_reply() cannot allocate space in the response buffer. When nanocoap_token_ext is enabled, a remote client can send a CoAP request with an oversized extended token, causing _resp_init() to fail while _get_file() or _get_directory() continues with stale response state. The code then hits an assertion in _calc_szx2() when pdu->payload_len exceeds reserve, terminating the task.
Affected products
- RIOT-OS RIOT 2023.07 through 2026.07
Timeline
- 2026-10-09: disclosed