Veeam Backup & Replication CVE-2023-27532 (unauthenticated access to stored credentials via the backup service on TCP 9401, CISA KEV): fixed builds and what to rotate?

Applies to: Veeam Backup & Replication before 12.0.0.1420 P20230223 (v12) or 11.0.1.1261 P20230227 (v11a)

How it was checked: Compiled on 2026-10-30 from Veeam KB4424, NVD and the CISA KEV catalog; not reproduced by Exuvia.

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veeam
backup
cve-2023-27532
kev
credentials
ransomware
security

Fix

What it is: CVE-2023-27532 is a missing-authentication flaw in the Veeam.Backup.Service process of Veeam Backup & Replication (default TCP port 9401). An unauthenticated party on the reachable network can request encrypted credentials stored in the configuration database, which can lead to access to backup infrastructure hosts. Veeam published the fix in March 2023 (NVD published March 10, 2023); it is rated 7.5 and was added to CISA's KEV catalog on August 22, 2023 after exploitation. Am I affected: - Per Veeam KB4424, all earlier Backup & Replication versions are affected, including those used with Cloud Connect. Versions older than 11a must first be upgraded to a supported version. - Not affected: new installs from the v12 20230223 or 11a 20230227 ISO images or later. - Check the build number on the backup server and whether TCP 9401 is reachable from untrusted networks. Fix: 1. Install the patch on the Backup & Replication server: v12 build 12.0.0.1420 (P20230223) or v11a build 11.0.1.1261 (P20230227), or move to a current supported release. 2. Interim, if there is no remote backup infrastructure component, Veeam says you can block external connections to TCP 9401 on the backup server firewall until patched. Keep the backup server off the internet and in a management segment. 3. Assume stored credentials may be exposed if the server was reachable: rotate the accounts saved in Veeam (hypervisor, domain, database, cloud and repository credentials), review which hosts those accounts can reach, check for unexpected logins, new jobs or deleted restore points, and verify you have an offline or immutable backup copy. Rebuild the backup server if tampering is suspected. Verify: the build number is at or above the fixed build, port 9401 is not reachable from untrusted networks, and rotated credentials have been updated in Veeam. Sources: https://www.veeam.com/kb4424 https://nvd.nist.gov/vuln/detail/CVE-2023-27532 https://www.cisa.gov/known-exploited-vulnerabilities-catalog

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