Security readout for executives and security teams
Plain-English summary
This flaw can let an unauthenticated remote attacker crash MPLS OAM handling on Cisco NX-OS devices. Repeated crashes can force a device reload, disrupting network availability. The business impact is outage risk on networks using MPLS-enabled NX-OS interfaces, not data theft or system takeover based on supplied sources.
Executive priority
Treat this as a high-priority availability risk where Cisco NX-OS supports MPLS forwarding. It is most urgent for networks where a device reload could interrupt customer, datacenter, or backbone connectivity. If MPLS is not used or not exposed, urgency is lower after validation.
Technical view
CVE-2021-1588 is an improper input validation flaw in Cisco NX-OS MPLS OAM processing. Malicious MPLS echo-request or echo-reply packets sent to an interface enabled for MPLS forwarding can crash and restart the MPLS OAM process repeatedly, causing device reload and DoS. CVSS v3.1 is 8.6 with network, low-complexity, unauthenticated attack conditions.
Likely exposure
Exposure is likely limited to Cisco NX-OS devices with interfaces enabled for MPLS forwarding. The supplied data does not identify specific NX-OS versions, platforms, or default configurations, so teams must confirm applicability against Cisco’s advisory and their device inventory.
Exploitation context
The supplied sources do not state active exploitation, and the CVE is not marked KEV. Exploitation requires network reachability to an MPLS-forwarding interface and malicious MPLS echo-request or echo-reply packets. Successful exploitation affects availability only according to the CVSS vector.
Researcher notes
Key unknowns in the supplied bundle are exact affected releases, fixed releases, and whether Cisco lists workarounds. The vulnerability maps to CWE-126 and has CVSS scope changed with high availability impact. Analysis should stay focused on MPLS OAM packet handling and exposure of MPLS-forwarding interfaces.
Mitigation direction
- Review Cisco’s advisory for affected platforms, releases, and fixed software guidance.
- Inventory Cisco NX-OS devices running MPLS forwarding on any interface.
- Prioritize remediation for core, edge, or provider-facing MPLS devices.
- Restrict untrusted reachability to MPLS-enabled interfaces where operationally possible.
- Monitor vendor guidance if affected version details remain unclear.
Validation and detection
- Compare NX-OS device inventory against Cisco’s advisory applicability criteria.
- Identify interfaces enabled for MPLS forwarding and MPLS OAM exposure.
- Check device logs for MPLS OAM process crashes or unexpected reloads.
- Confirm current NX-OS release status against Cisco’s fixed software guidance.
- Avoid production validation using crafted MPLS OAM traffic.
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-126: 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-2021-1588 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
- 8.6 (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: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:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.6HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210825 Cisco NX-OS Software MPLS OAM 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.
Buffer Over-read
Buffer Over-read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.