Security readout for executives and security teams
Plain-English summary
Certain Dell PowerEdge servers with NVDIMM-N installed have a BIOS-level memory handling flaw. A highly privileged local attacker could potentially cause service disruption, expose information, or run code before the operating system fully starts.
Executive priority
Handle through prioritized firmware risk management, not panic response. Focus first on production or sensitive-data servers that match both the model list and NVDIMM-N condition.
Technical view
CVE-2021-21555 is a CWE-122 heap-based buffer overflow in Dell PowerEdge BIOS affecting listed R640, R740, R740XD, R840, R940, R940xa, MX740c, MX840c, and T640 systems with NVDIMM-N installed. CVSS 3.1 is 6.1: local, low complexity, high privileges, user interaction required.
Likely exposure
Exposure appears limited to the listed Dell PowerEdge models with NVDIMM-N installed and affected BIOS. The supplied sources do not establish exposure for other Dell systems or systems without NVDIMM-N.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. Exploitation requires local high privileges and user interaction, reducing remote attack likelihood but keeping risk relevant for shared or heavily administered servers.
Researcher notes
The provided data identifies impact and prerequisites but does not include fixed BIOS versions or detailed Dell mitigation text. Avoid broad assumptions beyond Dell PowerEdge BIOS systems with NVDIMM-N installed.
Mitigation direction
- Inventory listed Dell PowerEdge models in server environments.
- Confirm whether each candidate system has NVDIMM-N installed.
- Check Dell advisory 000187958 for vendor remediation guidance.
- Apply Dell-supported BIOS updates or mitigations where applicable.
- Restrict local privileged access to trusted administrators.
Validation and detection
- Match asset model names against the affected Dell server list.
- Verify NVDIMM-N presence through hardware inventory or management tooling.
- Compare installed BIOS versions with Dell advisory guidance.
- Confirm remediation status in change and asset records.
- Review privileged local access paths on affected servers.
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-122: 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-21555 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
- 6.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:H/I:H/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:L/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:L0.65.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.1MediumVector: CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://www.dell.com/support/kbdoc/000187958CVE reference · x_refsource_MISC
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.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.