How severe is CVE-2021-21556?

CVE-2021-21556 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over local access with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is high, integrity high, and availability low.

Is CVE-2021-21556 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21556?

CVE-2021-21556 primarily affects Dell Poweredge R640 Firmware. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-21556?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-21556 published?

CVE-2021-21556 was published on 2021-06-14 and last updated on 2026-06-17.

CVE-2021-21556

CVE-2021-21556 is a medium-severity vulnerability in Dell Poweredge R640 Firmware with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 7.2
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Dell Poweredge R640 Firmware
Published: 2021-06-14
Last modified: 2026-06-17

Description

Dell PowerEdge R640, R740, R740XD, R840, R940, R940xa, MX740c, MX840c, and T640 Server BIOS contain a stack-based buffer overflow vulnerability in systems with NVDIMM-N installed. A local malicious user with high privileges may potentially exploit this vulnerability, leading to a denial of Service, arbitrary code execution, or information disclosure in UEFI or BIOS Preboot Environment.

Frequently asked questions

What is CVE-2021-21556?: Dell PowerEdge R640, R740, R740XD, R840, R940, R940xa, MX740c, MX840c, and T640 Server BIOS contain a stack-based buffer overflow vulnerability in systems with NVDIMM-N installed. A local malicious user with high privileges may potentially exploit this vulnerability, leading to a denial of Service, arbitrary code execution, or information disclosure in UEFI or BIOS Preboot Environment.
How severe is CVE-2021-21556?: CVE-2021-21556 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over local access with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is high, integrity high, and availability low.
Is CVE-2021-21556 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21556?: CVE-2021-21556 primarily affects Dell Poweredge R640 Firmware. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-21556?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21556 published?: CVE-2021-21556 was published on 2021-06-14 and last updated on 2026-06-17.

References

https://www.dell.com/support/kbdoc/000187958

Affected products (9)

cpe:2.3:o:dell:poweredge_r640_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_r740_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_r740xd_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_r940_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_r840_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_r940xa_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_t640_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_mx740c_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:dell:poweredge_mx840c_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Dell Poweredge R640 Firmware

CVE-2023-32460 — High (CVSS 8.8): Dell PowerEdge BIOS contains an improper privilege management security vulnerability. An unauthenticated local attacker…
CVE-2021-21557 — High (CVSS 8.1): Dell PowerEdge Server BIOS and select Dell Precision Rack BIOS contain an out-of-bounds array access vulnerability. A…
CVE-2024-0172 — High (CVSS 7.9): Dell PowerEdge Server BIOS and Dell Precision Rack BIOS contain an improper privilege management security…
CVE-2024-0161 — High (CVSS 7.2): Dell PowerEdge Server BIOS and Dell Precision Rack BIOS contain an Improper SMM communication buffer verification…
CVE-2023-25537 — Medium (CVSS 6.1): Dell PowerEdge 14G server BIOS versions prior to 2.18.1 and Dell Precision BIOS versions prior to 2.18.2, contain an…
CVE-2021-21555 — Medium (CVSS 6.1): Dell PowerEdge R640, R740, R740XD, R840, R940, R940xa, MX740c, MX840c, and T640 Server BIOS contain a heap-based buffer…

All CVEs affecting Dell Poweredge R640 Firmware →

Other CWE-787 (Out-of-bounds Write) vulnerabilities

CVE-2026-42369 — Critical (CVSS 10.0): GV-VMS V20 is a Video Monitoring Software used to gather the feeds of many surveillance cameras and manage other…
CVE-2026-4746 — Critical (CVSS 10.0): Out-of-bounds Write vulnerability in timeplus-io proton (base/poco/Foundation/src‎ modules). This vulnerability is…
CVE-2025-43300 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 15.8.5 and iPadOS…
CVE-2025-24201 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved checks to prevent unauthorized actions. This issue is fixed in…
CVE-2024-42479 — Critical (CVSS 10.0): llama.cpp provides LLM inference in C/C++. The unsafe `data` pointer member in the `rpc_tensor` structure can cause…
CVE-2024-39791 — Critical (CVSS 10.0): Stack-based buffer overflow vulnerabilities affecting Vonets industrial wifi bridge relays and wifi bridge…

Browse all CWE-787 (Out-of-bounds Write) vulnerabilities →