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CVE-2021-21281

29
FAUCET Score

CVE-2021-21281 is a critical buffer overflow vulnerability affecting Contiki-NG versions prior to 4.6, an open-source operating system for IoT devices. An unvalidated data offset in TCP packets allows a remote attacker to trigger the overflow after a TCP socket is established. With a CVSS score of 9.8 (CRITICAL), this vulnerability poses a high risk of complete compromise (confidentiality, integrity, availability) with no user interaction required. While no public exploit code or active exploitation has been observed, and community discussion is minimal, users should update to Contiki-NG 4.6 or apply the provided patch immediately.

Impacted Technologies

VendorProductVersion(s)CPE
< 4.6CPE matchmatch criteria
cpe:2.3:o:contiki-ng:contiki-ng:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.0HIGH

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
4.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.92%
Probability of exploitation in next 30 days
EPSS Percentile
56.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0092 is in the 41st percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / contiki-ng/contiki-ng/pull/1366
PatchThird Party Advisory
github.com / contiki-ng/contiki-ng/security/advisories/GHSA-mc42-fqfr-h9fp
PatchThird Party Advisory