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RiotOperating system · Riot Os

CVE-2021-27427

CRITICAL · 9.8 CVSS v3.1 Published 2022-05-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
RIOT OS version 2020.01.1 is vulnerable to integer wrap-around in its implementation of calloc function, which can lead to arbitrary memory allocation, resulting in unexpected behavior such as a crash or a remote code injection/execution.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

RIOT OS version 2020.01.1 contains an integer wrap-around vulnerability in its calloc implementation. When calculating allocation size (nmemb * size), integer overflow can occur, allowing attackers to allocate small buffers while obtaining pointers to arbitrary memory regions, leading to crashes or remote code execution.

MitigationUpgrade RIOT OS to a version with patched integer overflow protection in calloc, or implement explicit overflow checks before multiplication in the calloc function to validate that nmemb * size does not exceed allocated bounds.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
RiotOperating system
Affected:= 2020.01.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if the system runs RIOT OS
    Check system documentation, firmware build files, or boot logs for 'RIOT' or 'RIOT OS' branding. For embedded devices, examine the firmware binary or build configuration files (e.g., Makefile, boards/$(BOARD)/include/periph_conf.h) for RIOT OS markers.
    Affected if The system is confirmed to be running RIOT OS as the operating system or firmware base.
  2. Determine the installed RIOT OS version
    Locate the version identifier in the firmware or build system. Check for a version.h file, a VERSION file in the RIOT repository, or the firmware metadata. Common paths:RIOT/pkg/lwip/src/include/lwip/opt.h, or inspect the compiled binary for string '2020.01.1'. On the target, if shell access exists, run 'BOARD' or 'VERSION' commands if available.
    Affected if The version string matches exactly '2020.01.1'.
  3. Verify calloc usage in the application
    Search the application source code or binary for calls to the calloc function. In source: grep -r 'calloc' *.c. In binary: strings firmware.bin | grep calloc or use objdump. The vulnerability triggers when calloc(nmemb, size) is invoked with large nmemb and size values.
    Affected if The application code makes any call to calloc().
  4. Check for integer overflow conditions in calloc invocations
    Review the application source for dynamic allocations where nmemb or size values are derived from external input, user data, or network packets. Look for patterns like calloc(count, item_size) where count or item_size come from untrusted sources (e.g., parsed data, sensor inputs).
    Affected if The application uses calloc with values that could cause nmemb * size to exceed SIZE_MAX.

You are affected if your system runs RIOT OS version 2020.01.1 and your application uses the calloc function, particularly with externally-controlled allocation parameters.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade RIOT OS to a version with patched integer overflow protection in calloc, or implement explicit overflow checks before multiplication in the calloc function to validate that nmemb * size does not exceed allocated bounds.

Fix this in Riot Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-27427 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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