Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:L) | Low privileges required |
| User interaction (UI:N) | No user interaction |
| Scope (S:C) | Scope changed: impact spreads beyond the component |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:H) | High availability impact |
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
About Veeam Backup & Replication
CVE-2026-21666 affects Veeam Backup & Replication, a product from Veeam. Before acting, confirm where Veeam Backup & Replication runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: A vulnerability allowing an authenticated domain user to perform remote code execution (RCE) on the Backup Server.
The weakness class is Improper Access Control. The software does not properly restrict who can use a resource.
Based on its CVSS vector, the flaw can be reached over the network, needs some level of access, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Veeam Backup & Replication |
| Affected versions | Veeam Backup & Replication from 12.0.0.1402 before 12.3.2.4465 |
| Published | Mar 12, 2026 |
| Last modified | Jun 17, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | support@hackerone.com |
How to detect it
- Inventory every instance of Veeam Backup & Replication and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Veeam Backup & Replication named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Veeam Backup & Replication to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-284: Improper Access Control More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
A vulnerability allowing an authenticated domain user to perform remote code execution (RCE) on the Backup Server.
This vulnerability allows a Backup Administrator to perform remote code execution (RCE) as the postgres user by sending a malicious password parameter.
This vulnerability allows a Backup or Tape Operator to perform remote code execution (RCE) as root by creating a malicious backup configuration file.
File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. In versions 2.61.2 and below, any unauthenticated visitor can register a full administrator account when self-registration (signup = true) is enabled and the default user permissions have perm.admin = true. The signup handler blindly applies all default settings (including Perm.Admin) to the new user without any server-side guard that strips admin from self-registered accounts. The signupHandler is supposed to create unprivileged accounts for new visitors. It contains no explicit user.Perm.Admin = false reset after applying defaults. If an administrator (intentionally or accidentally) configures defaults.perm.admin = true and also enables signup, every account created via the public registration endpoint is an administrator with full control over all files, users, and server settings. This issue has been resolved in version 2.62.0.
A vulnerability in the JCE editor extension for Joomla allows the creation of new editor profiles for unauthenticated users, ultimately resulting in PHP code upload and execution.
A flaw in Node.js's permission model allows Unix Domain Socket (UDS) connections to bypass network restrictions when `--permission` is enabled. Even without `--allow-net`, attacker-controlled inputs (such as URLs or socketPath options) can connect to arbitrary local sockets via net, tls, or undici/fetch. This breaks the intended security boundary of the permission model and enables access to privileged local services, potentially leading to privilege escalation, data exposure, or local code execution. * The issue affects users of the Node.js permission model on version v25. In the moment of this vulnerability, network permissions (`--allow-net`) are still in the experimental phase.
Earn your free CTEM certification.
Learn to scope, prioritize, validate and mobilize fixes for CVEs like CVE-2026-21666 with a free CTEM certification.
Beginner / Practitioner / Program Leader
Explore certifications