Security readout for executives and security teams
Plain-English summary
CVE-2021-1268 can let someone on the same management network trigger excessive IPv6 traffic against Cisco IOS XR devices. The main business risk is loss or degradation of management-plane network availability, especially where many IOS XR nodes share the same segment.
Executive priority
Treat this as a high-priority availability risk for network infrastructure management. Urgency depends on whether untrusted systems can reach IOS XR management networks and how many affected nodes share a segment.
Technical view
Cisco IOS XR Software incorrectly forwards IPv6 packets with an IPv6 node-local multicast group destination when received on management interfaces. An unauthenticated adjacent attacker could inject such traffic and cause an IPv6 flood on the management-interface network, potentially resulting in degradation or denial of service.
Likely exposure
Exposure is most likely where Cisco IOS XR management interfaces are connected to networks reachable by untrusted or weakly controlled adjacent systems, and where IPv6 is present on those management segments. Larger shared management segments could experience greater traffic impact.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. Exploitation requires adjacency to the management-interface network and does not require authentication or user interaction.
Researcher notes
The public description supports adjacent, unauthenticated DoS via IPv6 handling on management interfaces. It does not provide affected version detail in the bundle. Validate exposure through inventory, network adjacency, IPv6 presence, and Cisco advisory mapping.
Mitigation direction
- Review the Cisco advisory for affected releases, workarounds, and fixed software guidance.
- Prioritize vendor-recommended updates for exposed Cisco IOS XR management networks.
- Restrict management-interface network access to trusted administrative systems where feasible.
- Segment management networks to limit blast radius between IOS XR nodes.
- Monitor management segments for abnormal IPv6 multicast traffic or flooding.
Validation and detection
- Inventory Cisco IOS XR devices and their management-interface network placement.
- Check whether IPv6 is enabled or present on management-interface segments.
- Confirm untrusted systems cannot join the same management network segment.
- Review network telemetry for unusual IPv6 node-local multicast volume.
- Map deployed IOS XR versions against the Cisco advisory.
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-1076: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-1268 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
- 7.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/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:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H2.84Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.4HighVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210203 Cisco IOS XR Software IPv6 Flood Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
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.
Insufficient Adherence to Expected Conventions
Insufficient Adherence to Expected Conventions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.