Security readout for executives and security teams
Plain-English summary
CVE-2021-26735 is a Windows local privilege-escalation issue in Zscaler Client Connector installers and uninstallers before version 3.6. A local attacker could potentially get code running as SYSTEM, but the CVSS data indicates high attack complexity and required user interaction.
Executive priority
Treat this as a targeted endpoint hardening issue, not an internet-scale emergency. Remediate during normal endpoint maintenance unless sensitive workstations or shared Windows systems still carry pre-3.6 components.
Technical view
The issue is described as an unquoted/untrusted search path weakness while the Windows uninstaller executes REG DELETE. The attack is local, requires low privileges and user interaction, and can affect confidentiality, integrity, and availability if successfully triggered.
Likely exposure
Exposure is most likely on Windows endpoints using Zscaler Client Connector installer or uninstaller components before version 3.6. The provided affected-version metadata is limited, so validate against Zscaler’s release guidance.
Exploitation context
The source bundle does not identify active exploitation, and the CVE is not marked as CISA KEV. The vulnerability is local privilege escalation, not remote initial access, and requires a local adversary plus user interaction.
Researcher notes
The evidence supports local privilege escalation through installer/uninstaller path handling. No exploit details or public exploitation are provided. The bundle’s affected-product metadata is sparse, so version validation should rely on Zscaler’s release summary and asset inventory.
Mitigation direction
- Upgrade affected Windows Client Connector installer and uninstaller components to version 3.6 or later.
- Review Zscaler’s Client Connector release guidance for the supported remediation path.
- Remove obsolete pre-3.6 installer or uninstaller artifacts from managed endpoints.
- Prioritize endpoints where lower-privileged users can trigger install, uninstall, or upgrade workflows.
Validation and detection
- Inventory Windows endpoints for Zscaler Client Connector versions before 3.6.
- Check software deployment shares for retained pre-3.6 installer or uninstaller packages.
- Confirm current uninstall and upgrade workflows use patched Zscaler packages.
- Review endpoint telemetry for unusual SYSTEM-level process creation during Zscaler uninstall or upgrade activity.
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-346: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-26735 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
- Medium
- CVSS
- 6.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/PR:L/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:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H0.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.7MediumVector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
Source materials
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.
Origin Validation Error
Origin Validation Error represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.