Security readout for executives and security teams
Plain-English summary
This is a high-severity Dell server BIOS flaw. An attacker already holding high local privileges could abuse it to crash the system, expose sensitive information, or run code in a highly privileged firmware mode. It is not a remote internet-facing issue based on the provided sources.
Executive priority
Treat as a high-priority infrastructure hygiene issue, especially for critical servers. It is not described as remotely exploitable, but firmware-level impact and high confidentiality/integrity consequences justify timely vendor-guided remediation.
Technical view
CVE-2021-21557 is an out-of-bounds array access vulnerability in Dell PowerEdge Server BIOS and select Dell Precision Rack BIOS. Exploitation requires local access with high privileges and may affect System Management Mode, with possible denial of service, information disclosure, or arbitrary code execution. CVSS v3.1 score is 8.1.
Likely exposure
Exposure is limited to systems running affected Dell BIOS versions. The bundle identifies Dell PowerEdge BIOS Intel 15G and references select Dell Precision Rack BIOS, but does not provide exact version ranges.
Exploitation context
The provided data does not show CISA KEV listing or active exploitation. The attack requires a local malicious user with high privileges, reducing broad exposure but increasing concern on shared, administered, or previously compromised servers.
Researcher notes
Key constraints are AV:L and PR:H, with changed scope and high confidentiality/integrity impact. The vulnerability maps to CWE-20 and involves System Management Mode. The public bundle lacks exact version ranges and patch details, so validation depends on Dell advisory data.
Mitigation direction
- Check Dell advisory 000187958 for affected models, BIOS versions, and remediation guidance.
- Inventory Dell PowerEdge and Precision Rack systems against the advisory.
- Plan BIOS updates where Dell lists fixed versions for your hardware.
- Restrict and audit high-privilege local access on affected servers.
- Prioritize systems hosting sensitive workloads or shared administrative access.
Validation and detection
- Confirm each server model and BIOS version from asset inventory or management tooling.
- Compare observed BIOS versions with Dell advisory 000187958.
- Verify remediation status after any BIOS update or vendor-directed action.
- Review privileged local account activity on affected systems.
- Document unsupported, deferred, or exception-handled systems.
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-20: 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-2021-21557 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
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/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:N/S:C/C:H/I:H/A:L1.56Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/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.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.