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Vulnerability record · CVE-2026-19820 · published 1 September 2026

CVE-2026-19820: Link following vulnerability

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.

7.8 CVSS 4.0 High EPSS 0.33% · top 76.7% CWE-59 · Link following Deferred
7.8CVSS 4.0 base score
0.33%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
11 Sep 2026Last modified by NVD

Description

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.

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:

References

LinkTags
https://www.backblaze.com/computer-backup/docs/backup-client-release-notes-windows
https://www.backblaze.com/status/update

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-19820), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.