Veeam Backup for Microsoft 365 8.6 Patch 1 Fixes Four Flaws
Tech GuruQuick Answer
Veeam KB4957 fixes four vulnerabilities in Backup for Microsoft 365 8. Inventory exact builds and organization-transfer use, deploy 8.6 Patch 1 build 8.6.0.5011, validate tenancy and REST controls, and retain evidence.
Confirm Scope And Apply The Supported Remediation
What to do now: Inventory Backup for Microsoft 365 servers, exact builds, organization-transfer peers, Administrator roles, REST exposure, PostgreSQL service context, owners, and maintenance windows. Match each deployment to both fix boundaries and prerequisites; do not infer cross-tenant access without the organization-transfer peer path or extend affected versions beyond Veeam's statement. Upgrade to 8.6 Patch 1 build 8.6.0.5011, which is later than the 8.6.0.1102 boundary that fixes the first two CVEs. Confirm the running build, test backup, restore, organization transfer and REST workflows, review peer and administrative activity where warranted, verify jobs and repositories, and retain evidence.
Last verified: 2026-10-27 UTC. Recheck the authoritative advisory and supported distribution channel before changing production.
Scope And Authority
| Product scope | Veeam Backup for Microsoft 365 8 |
|---|---|
| Advisory | KB4957 |
| CVEs | CVE-2025-64394, CVE-2026-106076, CVE-2026-106077, CVE-2026-106078 |
| Authoritative release date | 2026-10-27 00:00:00 UTC |
| Authority revision date | 2026-10-27 00:00:00 UTC |
| Affected versions | Version 8 builds through 8.5.0.1014 for the SQL injection and arbitrary-file-read issues, and through 8.6.0.1102 for the REST authentication and installer issues; unsupported releases were not tested and Veeam says they should be considered vulnerable. |
| Fixed version | Veeam Backup for Microsoft 365 8.6 build 8.6.0.1102 for CVE-2026-106076/106077; 8.6 Patch 1 build 8.6.0.5011 for CVE-2026-106078 and CVE-2025-64394 |
| CVSS base score | 4.3 to 9.0 (CVSS v4.0) |
| CVSS severity | Medium to Critical |
| Exploitation status | Veeam does not state that these vulnerabilities are being maliciously exploited.; no exploitation claim is inferred. |
What Changed
Veeam fixed organization-transfer SQL injection with cross-tenant impact and code execution, privileged arbitrary file read, forged federation-token REST access, and installer privilege escalation.
What To Validate Now
- Inventory. Inventory Backup for Microsoft 365 servers, exact builds, organization-transfer peers, Administrator roles, REST exposure, PostgreSQL service context, owners, and maintenance windows.
- Establish applicability. Match each deployment to both fix boundaries and prerequisites; do not infer cross-tenant access without the organization-transfer peer path or extend affected versions beyond Veeam's statement.
- Remediate. Upgrade to 8.6 Patch 1 build 8.6.0.5011, which is later than the 8.6.0.1102 boundary that fixes the first two CVEs.
- Validate. Confirm the running build, test backup, restore, organization transfer and REST workflows, review peer and administrative activity where warranted, verify jobs and repositories, and retain evidence.
- Retain evidence. Preserve asset and owner identifiers, the applicability decision, before-and-after versions, change approval, installation output, validation results, and any exception or rollback record.
Operational Cautions
Installing base 8.6.0.1102 alone does not fix the REST authentication or installer issues; verify Patch 1 build 8.6.0.5011 or later explicitly.
Evidence To Retain
- Exact product, release stream, package or application version, enabled feature, environment, and accountable owner.
- UTC timestamps, authority revision, approved change record, installer or package-manager output, and resulting version.
- Relevant logs and monitoring evidence, test results, exceptions, compensating controls, and rollback decisions.
Related TechGeeks Resources
Authoritative References
Correction policy: If the authority changes affected versions, fixed versions, severity, exploitation information, mitigations, or required action, TechGeeks will update this notice and its verification date.
