EUVD-2026-68916
GHSA-wf7j-r93f-5cvm
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Local attack vector and high complexity because OS security controls must be pre-disabled by an admin; low privileges for the exploiting user; scope change since Windows OS boot integrity is impacted.
Primary rating from Vendor (Bugcrowd).
CVSS VectorVendor: Bugcrowd
Lifecycle Timeline
8DescriptionCVE.org
A vulnerability in the Backblaze Client allows a local user to make the system not bootable by creating a link from Backblaze's folder to Windows OS system files during a backup. Successful exploitation requires an administrator-level system change that results in the absence of specific Windows OS security controls. This vulnerability is due to improper link resolution.
AnalysisAI
Improper link resolution in the Backblaze Client for Windows allows a local user to render a system unbootable by creating a junction or symbolic link from Backblaze's backup folder to critical Windows OS system files, which the backup process then processes without adequate validation. The vulnerability is scoped to Windows deployments where specific OS-level security controls have been disabled through an administrator-level change. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local access to the Windows system running the Backblaze Client and the ability to create filesystem junctions or symbolic links within Backblaze's backup folder. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The provided CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) is directly contradicted by the vulnerability description, which explicitly states that exploitation requires a local user and an administrator-level system change to remove specific Windows security controls - making the Network attack vector and no-privileges metrics clearly erroneous. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Monitor the Backblaze Windows Client release notes at https://www.backblaze.com/computer-backup/docs/backup-client-release-notes-windows for a patched release version; no specific fixed version is confirmed in the available data. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Windows systems running Backblaze Client and audit which have disabled OS-level security controls through administrative configuration. …
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Backblaze for Windows and Backblaze for macOS before 7.0.0.439 suffer from improper privilege management in `bztransmit`
Backblaze for Windows before 7.0.1.433 and Backblaze for macOS before 7.0.1.434 suffer from improper certificate validat
B2 Command Line Tool is the official command line tool for the backblaze cloud storage service. Rated medium severity (C
b2-sdk-python is a python library to access cloud storage provided by backblaze. Rated medium severity (CVSS 4.7).
Same weakness CWE-59 – Improper Link Resolution Before File Access
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External POC / Exploit Code
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