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CVE Record

CVE-2021-27138: The boot loader in Das U-Boot before 2021.04-rc2 mishandles use of unit addresses in a FIT.

The boot loader in Das U-Boot before 2021.04-rc2 mishandles use of unit addresses in a FIT.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Das U-Boot boot loader versions before 2021.04-rc2 mishandle unit addresses in FIT boot images. A successful attack could compromise confidentiality, integrity, and availability during boot, but the CVSS data indicates local access and user interaction are required.

Executive priority

Prioritize assets where physical access, removable boot media, field servicing, or firmware update workflows could expose the boot chain. Treat unknown bootloader provenance as a risk requiring vendor confirmation.

Technical view

CVE-2021-27138 is a high-severity Das U-Boot FIT handling flaw fixed before or at 2021.04-rc2, with upstream commits cited. CVSS 3.1 is 7.8: local attack vector, low complexity, no privileges, user interaction required, and high CIA impact.

Likely exposure

Exposure is most likely in embedded, appliance, or firmware environments that include Das U-Boot before 2021.04-rc2 and can be made to load attacker-influenced FIT boot images.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation. The CVSS vector suggests exploitation requires local access and user interaction, limiting remote mass exploitation but still raising supply-chain and device-tampering concern.

Researcher notes

Evidence is limited to the CVE description, CVSS vector, upstream commits, and a Debian LTS reference. The bundle does not provide exploit details, CWE classification, or a vendor-specific affected product matrix.

Mitigation direction

  • Upgrade Das U-Boot to 2021.04-rc2 or later where applicable.
  • Apply vendor or distribution firmware updates that include the cited upstream fixes.
  • Check Debian LTS guidance if using Debian-packaged U-Boot.
  • Restrict who can modify boot media, firmware images, or boot configuration.
  • Confirm device vendors have backported the relevant U-Boot commits.

Validation and detection

  • Inventory products and firmware builds that include Das U-Boot.
  • Determine whether each build is before 2021.04-rc2 or includes backports.
  • Review boot image handling paths that load FIT images.
  • Check vendor advisories or SBOMs for the cited commit identifiers.
  • Document devices where bootloader version cannot be confirmed.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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.

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CVE-2021-27138 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AC:L/AV:L/A:H/C:H/I:H/PR:N/S:U/UI:R

Official CVE source material

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.

1CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AC:L/AV:L/A:H/C:H/I:H/PR:N/S:U/UI:R1.85.9Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2021-27138Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AC:L/AV:L/A:H/C:H/I:H/PR:N/S:U/UI:R

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.