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TI-2026-70118 Aliases CVE-2026-107838

Unchecked error in RIOT nanocoap_fileserver allows reachable assertion

Priority LOW 39CWE-252Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-617.

Summary

RIOT versions from 2023.07 through 2026.07 ignore a failed response header setup in nanocoap_fileserver (CWE-252). An unauthenticated remote attacker can send a CoAP request with a large extended token when nanocoap_token_ext is enabled, so _get_file() or _get_directory() continues with stale response state. This reaches a reachable assertion (CWE-617) that terminates the affected service or device task.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00339 27th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
RIOT-OSRIOT2023.07 – 2026.07—No fix listedCNA
  • RIOT VendorRIOT-OS Affected 2023.07 – 2026.07 Fixed in — No fix listed CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:o:riot-os:riot:*:*:*:*:*:*:*:*——RIOT-OS
  • cpe:2.3:o:riot-os:riot:*:*:*:*:*:*:*:* Versions — — ·RIOT-OS

Remediation

No fixed release of RIOT is listed as of this review.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Timeline

  1. 2026-10-10 Threatist record created from CVE-2026-107838
  2. 2026-10-11 Priority changed: MEDIUM → LOW
  3. 2026-10-13 CISA SSVC decision points changed

References

Other 3

  • TI-2024-21112 Buffer overflows in RIOT CVSS 3.1CRITICAL 9.8
  • TI-2023-16843 RIOT-OS vulnerable to Out of Bounds Write in _rbuf_add CVSS 3.1CRITICAL 9.8
  • TI-2023-10319 RIOT-OS vulnerable to Buffer Overflow during IPHC receive CVSS 3.1CRITICAL 9.8
  • TI-2026-22079 RIOT has an Out-of-Bounds Write in nanoCoAP Handler CVSS 3.1CRITICAL 9.8
  • TI-2023-16842 RIOT-OS vulnerable to Race Condition in SFR Timeout CVSS 3.1HIGH 7.5
  • TI-2023-16841 RIOT-OS vulnerable to NULL pointer dereference during NHC encoding CVSS 3.1HIGH 7.5
See all 45 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences