Security readout for executives and security teams
Plain-English summary
Dell EMC Avamar Server 19.3 and 19.4 have a web UI authorization flaw. A remote user with low privileges could access or modify other users' backup data without authorization. This is serious because backup systems often contain sensitive copies of business data and are critical to recovery.
Executive priority
Treat as high priority for backup environments. Backup data confidentiality and recovery trust are at risk, but the provided evidence does not support active exploitation or emergency zero-day handling.
Technical view
CVE-2021-21511 is a CWE-285 improper authorization issue in Dell EMC Avamar Server web UI versions 19.3 and 19.4. CVSS 3.1 is 8.1: network exploitable, low complexity, low privileges required, no user interaction, high confidentiality and integrity impact, no availability impact.
Likely exposure
Exposure is limited to Dell EMC Avamar Server 19.3 or 19.4 deployments, especially where the web UI is reachable by many internal users or remote low-privileged accounts.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation requires remote access and a low-privileged account. The main risk is unauthorized reading or modification of other users' backup data.
Researcher notes
The source bundle does not include fixed version details or workaround specifics beyond the Dell advisory reference. Avoid assuming affected products outside Avamar Server 19.3 and 19.4. Focus validation on versioning, web UI reachability, account scope, and audit evidence.
Mitigation direction
- Identify any Dell EMC Avamar Server 19.3 or 19.4 instances.
- Review Dell advisory DSA-2021-033 for supported remediation guidance.
- Restrict Avamar web UI access to trusted networks and approved administrators.
- Review user roles and remove unnecessary low-privileged accounts.
- Increase monitoring for unusual backup data access or modification.
Validation and detection
- Confirm Avamar Server version on every backup management instance.
- Verify web UI access is not broadly exposed.
- Confirm Dell-recommended remediation has been applied where applicable.
- Review audit logs for unusual cross-user backup data access.
- Validate role boundaries using approved administrative testing only.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-285: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-21511 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N2.85.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.dell.com/support/kbdoc/en-us/000182926/dsa-2021-033-dell-emc-avamar-server-improper-authorization-vulnerabilityCVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Authorization
Improper Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.