CVE-2021-21280Public exploitNetwork attack vector

Memory corruption via unchecked extension-header length

Published Jun 18, 2021 · Updated Aug 3, 2024

Out-of-bounds write in Contiki-NG before 4.6 allows remote attackers to corrupt memory via a crafted 6LoWPAN extension-header chain. In os/net/ipv6/sicslowpan.c, memcpy uses a packet-controlled len value to copy hc06_ptr data into the uncompressed packet buffer without checking remaining space. Network access to the device's 6LoWPAN input path is sufficient, and the resulting overwrite compromises data or interrupts the device.

CVSS severity8.6
High
EPSS probability1.06%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Contiki-NG before 4.6 allows remote attackers to corrupt memory via a crafted 6LoWPAN extension-header chain. In os/net/ipv6/sicslowpan.c, memcpy uses a packet-controlled len value to copy hc06_ptr data into the uncompressed packet buffer without checking remaining space. Network access to the device's 6LoWPAN input path is sufficient, and the resulting overwrite compromises data or interrupts the device.

The record

CVE
CVE-2021-21280
Published
Jun 18, 2021
Updated
Aug 3, 2024
Vendor
Contiki-NG
Product
Contiki-NG
Classifications
CWE-787
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Contiki-NG · Contiki-NGversion=< 4.6

Published CVSS scores

8.6GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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