{"id":"CVE-2021-21280","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-21280","generatedAt":"2026-10-28T02:58:49.795Z","title":"It is possible to cause an out-of-bounds write in versions of Contiki-NG prior to 4.6 when transmitting a 6LoWPAN packet with a chain of extension headers.","description":"Contiki-NG is an open-source, cross-platform operating system for internet of things devices. It is possible to cause an out-of-bounds write in versions of Contiki-NG prior to 4.6 when transmitting a 6LoWPAN packet with a chain of extension headers. Unfortunately, the written header is not checked to be within the available space, thereby making it possible to write outside the buffer. The problem has been patched in Contiki-NG 4.6. Users can apply the patch for this vulnerability out-of-band as a workaround.","published":"2021-06-18T21:15:08.000Z","lastModified":"2026-06-17T03:35:11.000Z","status":"Modified","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-787"],"affected":["contiki-ng/contiki-ng"],"epss":{"score":0.01064,"percentile":0.64419,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (1.06%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/contiki-ng/contiki-ng/pull/1409","tags":["Patch","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/contiki-ng/contiki-ng/security/advisories/GHSA-r768-hrhf-v592","tags":["Exploit","Patch","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/contiki-ng/contiki-ng/pull/1409","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/contiki-ng/contiki-ng/security/advisories/GHSA-r768-hrhf-v592","tags":["Exploit","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-21280","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}