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CVE-2026-27703

RIOT has an Out-of-Bounds Write in nanoCoAP Handler

High7.5Public exploitEPSS 0.55%
Published
Updated
Reserved
Assigned by
GitHub_M

Description

RIOT is an open-source microcontroller operating system, designed to match the requirements of Internet of Things (IoT) devices and other embedded devices. In 2026.01 and earlier, the default handler for the well_known_core resource coap_well_known_core_default_handler writes user-provided option data and other data into a fixed size buffer without validating the buffer is large enough to contain the response. This vulnerability allows an attacker to corrupt neighboring stack location, including security-sensitive addresses like the return address, leading to denial of service or arbitrary code execution.

Public exploit

An exploit or proof of concept is public: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.

Timeline

  1. ID reserved

    By GitHub_M

  2. · 16 days later

    Published

  3. · 1 day later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-27703, by who scored it
Scored byCVSSScoreVector
GitHub_MCNA (assigner)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVDNVD · Analyzed3.1Critical9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (exploitation in 30 days)
0.55% · top 54% of all CVEs (7 Nov 2026)
CISA SSVC
Exploitation: poc · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

Affected products

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .