Security readout for executives and security teams
Plain-English summary
CVE-2021-1229 can let a remote unauthenticated attacker slowly exhaust memory on Cisco NX-OS devices by abusing ICMPv6 handling on IPv6-configured interfaces. The expected impact is traffic instability and loss of ICMPv6 processing, not data theft. Recovery may require a device reboot.
Executive priority
Treat as a moderate operational resilience issue for network infrastructure. Prioritize externally or broadly reachable IPv6-enabled NX-OS devices, especially where instability would affect critical routing, switching, or data center services.
Technical view
Cisco reports improper error handling in NX-OS ICMPv6 processing. Sustained crafted ICMPv6 packets sent to a local IPv6 address can cause a slow memory leak in the ICMPv6 process, eventually leading it to run out of memory and stop processing ICMPv6 traffic.
Likely exposure
Exposure is most likely on Cisco NX-OS devices with IPv6-configured interfaces reachable by untrusted or poorly filtered network sources. The source bundle does not identify specific affected NX-OS versions.
Exploitation context
The CVE record describes unauthenticated remote exploitation with low attack complexity, but only availability impact. The source bundle does not cite active exploitation, public exploit use, or CISA KEV listing.
Researcher notes
Evidence supports a slow memory leak DoS in ICMPv6 processing, categorized as CWE-401. The bundle lacks affected version granularity, fixed-release details, workaround specifics, and exploitation telemetry, so validation should start with Cisco advisory mapping.
Mitigation direction
- Inventory Cisco NX-OS devices with IPv6-configured interfaces.
- Review Cisco advisory for affected releases and remediation guidance.
- Restrict untrusted IPv6 traffic to device local addresses where feasible.
- Monitor ICMPv6 process memory and traffic instability indicators.
- Plan reboot recovery procedures for impacted devices.
Validation and detection
- Confirm whether NX-OS devices have IPv6 enabled on interfaces.
- Map running NX-OS versions against Cisco advisory guidance.
- Review telemetry for ICMPv6 process memory growth.
- Check for unexplained ICMPv6 packet drops or traffic instability.
- Verify compensating controls limit untrusted IPv6 reachability.
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-401: 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-2021-1229 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
- Medium
- CVSS
- 5.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
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:C/C:N/I:N/A:L3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.8MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- 20210224 Cisco NX-OS Software ICMP Version 6 Memory Leak 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.
Missing Release of Memory after Effective Lifetime
Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.