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CVE Record

CVE-2022-28735: The GRUB2's shim_lock verifier allows non-kernel files to be loaded on shim-powered secure boot systems.

The GRUB2's shim_lock verifier allows non-kernel files to be loaded on shim-powered secure boot systems. Allowing such files to be loaded may lead to unverified code and modules to be loaded in GRUB2 breaking the secure boot trust-chain.

MediumCVSS 6.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This vulnerability weakens the Secure Boot chain on systems that use GRUB2 with shim. A highly privileged local attacker could cause GRUB2 to load files that were not properly verified as kernels, potentially allowing untrusted code or modules before the operating system fully starts.

Executive priority

Treat this as a moderate-priority boot-chain integrity issue. It is not shown as remotely exploitable or actively exploited in the provided sources, but it matters where Secure Boot underpins compliance, anti-tamper controls, or endpoint trust.

Technical view

GRUB2's shim_lock verifier can allow non-kernel files to be loaded on shim-powered Secure Boot systems. The CVSS vector is local, low complexity, high privileges, no user interaction, with high confidentiality, integrity, and availability impact. The source bundle does not identify specific fixed versions.

Likely exposure

Exposure is most likely on Linux or appliance platforms using GNU GRUB/grub2 with shim-based UEFI Secure Boot. The provided affected-version data is incomplete, so distribution and vendor advisories must determine actual exposure.

Exploitation context

The bundle does not show CISA KEV listing or other evidence of active exploitation. Exploitation is local and requires high privileges, limiting broad remote risk but increasing concern for persistence, boot integrity, and regulated environments.

Researcher notes

Evidence supports a shim_lock verification flaw in GRUB2 that can break the Secure Boot trust chain. The provided data does not include CWE mapping, precise vulnerable versions, fixed versions, or exploit-in-the-wild confirmation, so validation should remain vendor-specific.

Mitigation direction

  • Check OS, appliance, and GRUB2 vendor advisories for fixed packages or bootloader updates.
  • Prioritize systems relying on Secure Boot for trust, compliance, or tamper resistance.
  • Apply vendor-approved GRUB2, shim, and firmware-related updates when available.
  • Follow vendor guidance for Secure Boot database or bootloader remediation steps.
  • Review appliance advisories, including NetApp guidance where relevant to deployed products.

Validation and detection

  • Inventory systems using GNU GRUB/grub2 with shim-powered UEFI Secure Boot.
  • Confirm installed bootloader packages against vendor advisory fixed-version guidance.
  • Verify Secure Boot is enabled only with trusted, vendor-supported boot components.
  • Check vulnerability management tools for CVE-2022-28735 findings on Linux and appliances.
  • Document unsupported systems where vendor exposure or fixes remain unclear.
Prepared
Confidence
medium
Sources
5

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.

ATT&CK lookup starting points

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CVE-2022-28735 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
Medium
CVSS
6.7 (3.1)
Known Exploited
No
Published

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

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
4Source 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
6.7CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H0.85.9Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

6.7Medium
CVSS 3.1 vector shape for CVE-2022-28735Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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
GNU ProjectGNU GRUBgrub2, 0Listed
Weakness

CWE details

No CWE listed

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