CVE-2026-19820

Unbootable system via improper link resolution

Published Sep 1, 2026 · Updated Sep 1, 2026

Improper link resolution in Backblaze Computer Backup Client 10.0.0.1029, 10.0.1.10307, and 10.0.2.1047 allows local users to prevent booting. During a backup, the Windows client follows a crafted link from its folder to protected operating-system files instead of rejecting the redirect. Exploitation requires an administrator-level system change that removes specific Windows security controls, after which local users can leave the host unbootable.

CVSS severityUnavailable
Unscored
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper link resolution in Backblaze Computer Backup Client 10.0.0.1029, 10.0.1.10307, and 10.0.2.1047 allows local users to prevent booting. During a backup, the Windows client follows a crafted link from its folder to protected operating-system files instead of rejecting the redirect. Exploitation requires an administrator-level system change that removes specific Windows security controls, after which local users can leave the host unbootable.

The record

CVE
CVE-2026-19820
Published
Sep 1, 2026
Updated
Sep 1, 2026
Vendor
Backblaze
Product
Backblaze Computer Backup Client
Classifications
CWE-59, T1485
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.0.1029
  2. Affected versionversion=10.0.1.10307
  3. Affected versionversion=10.0.2.1047

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Backblaze · Backblaze Computer Backup Clientversion=10.0.0.1029; version=10.0.1.10307; version=10.0.2.1047

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-59Improper Link Resolution Before File Access ('Link Following')
T1485Data Destruction

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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