Security readout for executives and security teams
Plain-English summary
Dell EMC NetWorker Management Console clients may fail to properly validate certificates when connecting over SSL to the application server. A nearby unauthenticated attacker on the same network collision domain could potentially intercept or alter that management traffic. This is most urgent where backup administration occurs on shared or poorly segmented networks.
Executive priority
Treat this as a high-priority backup-platform risk, especially if backup administrators connect from shared networks. The issue can affect confidentiality and integrity of management traffic, but available evidence does not support emergency treatment based on active exploitation.
Technical view
CVE-2021-21559 is a CWE-295 improper certificate validation flaw in Dell EMC NetWorker client components, specifically NetWorker Management Console communication with the application server. The CVSS 3.1 score is 7.1, with adjacent-network access, high attack complexity, no privileges, and user interaction required. Confidentiality, integrity, and availability impacts are rated high.
Likely exposure
Exposure is likely limited to environments running Dell EMC NetWorker 18.x, 19.1.x, 19.2.x, 19.3.x, 19.4, or 19.4.0.1 where administrators use NetWorker Management Console over networks an attacker could share or influence.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. Exploitation requires an attacker in the same network collision domain as the client and successful man-in-the-middle positioning, making exposure highly dependent on network topology and administrative workstation placement.
Researcher notes
Focus analysis on certificate validation behavior in the NetWorker Management Console client path. The source bundle does not provide fixed version details, exploit proof, or detailed indicators. Avoid assuming server-side exposure beyond the described client-to-application-server SSL communication path.
Mitigation direction
- Review Dell DSA-2021-104 and apply the vendor-recommended NetWorker security update.
- Prioritize backup administration networks with shared, flat, or weakly controlled access.
- Restrict NetWorker Management Console client-to-server paths to trusted management networks.
- Avoid using the console from untrusted or guest-accessible network segments.
- Check Dell guidance for any version-specific upgrade or workaround requirements.
Validation and detection
- Inventory deployed Dell EMC NetWorker versions and identify affected 18.x and 19.x releases.
- Confirm whether NetWorker Management Console is used in the environment.
- Map client-to-application-server network paths for shared collision-domain exposure.
- Verify remediation status against Dell DSA-2021-104, not only package age.
- Review administrative network segmentation and access controls around backup systems.
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
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-295: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-21559 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
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:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H1.25.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.1HighVector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.dell.com/support/kbdoc/en-us/000186638/dsa-2021-104-dell-emc-networker-security-update-for-multiple-vulnerabilitiesCVE 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 Certificate Validation
Improper Certificate Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.