Backblaze Personal Computer Backup bzserv Link Following Denial-of-Service Vulnerability

September 9th, 2026
ZDI-26-625 ZDI-CAN-29324

CVE ID

CVE-2026-19820

CVSS Score

6.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

Affected Vendors

Backblaze

Affected Products

Personal Computer Backup

Vulnerability Details

This vulnerability allows local attackers to create a denial-of-service condition on affected installations of Backblaze Personal Computer Backup. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the Backblaze Service. By creating a symbolic link, an attacker can abuse the service to overwrite arbitrary files. An attacker can leverage this vulnerability to create a denial-of-service condition on the system.

Additional Details

Fixed in Release Version 10.0.1.1069 (https://www.backblaze.com/computer-backup/docs/backup-client-release-notes-windows)


Disclosure Timeline

  • 2026-04-07 - Vulnerability reported to vendor
  • 2026-09-09 - Coordinated public release of advisory
  • 2026-09-09 - Advisory Updated

Credit

hamdi

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