Security readout for executives and security teams
Plain-English summary
CVE-2021-21279 can let an unauthenticated network attacker stall affected Contiki-NG IoT devices by triggering an infinite loop in IPv6 neighbor solicitation handling. The business impact is availability loss, not data theft. A fix is available in Contiki-NG 4.6.
Executive priority
Treat this as a high-priority availability risk for affected IoT fleets. Patch planning should focus on operationally important devices, exposed IPv6 environments, and products where service interruption creates safety, business continuity, or support impact.
Technical view
Contiki-NG versions before 4.6 contain CWE-835 infinite-loop behavior while processing IPv6 Neighbor Solicitation messages. Because Contiki-NG uses cooperative scheduling for core system and communication stack work, the loop can deny service to the device. CVSS 3.1 is 7.5, reflecting network attackability and high availability impact.
Likely exposure
Exposure is most likely in IoT products or firmware built on Contiki-NG before 4.6, especially where affected IPv6 networking is reachable from untrusted or adjacent network paths. The provided sources do not identify specific downstream products or deployments.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Public details support a denial-of-service condition, but not confidentiality or integrity compromise.
Researcher notes
The key technical issue is an infinite loop during IPv6 NS processing in a cooperatively scheduled OS. Validation should focus on version provenance, patched code lineage, and safe availability regression testing. The provided evidence does not establish active exploitation or downstream vendor impact.
Mitigation direction
- Upgrade Contiki-NG deployments to version 4.6 or later.
- Apply the vendor out-of-band patch where immediate upgrade is impractical.
- Prioritize devices with exposed or untrusted IPv6 network adjacency.
- Review product firmware dependencies for embedded Contiki-NG before assuming non-exposure.
Validation and detection
- Inventory firmware and SBOMs for Contiki-NG versions before 4.6.
- Confirm vendor patches or Contiki-NG 4.6 are present in shipped images.
- Check regression coverage for IPv6 Neighbor Solicitation handling without system hangs.
- Assess whether affected devices are reachable from untrusted IPv6 networks.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-835: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-21279 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/contiki-ng/contiki-ng/security/advisories/GHSA-rr5j-j8m8-fc4fCVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Loop with Unreachable Exit Condition ('Infinite Loop')
Loop with Unreachable Exit Condition ('Infinite Loop') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.