Security readout for executives and security teams
Plain-English summary
CVE-2021-26736 affects older Zscaler Client Connector installer and uninstaller components on Windows. A local attacker with limited access may be able to get SYSTEM-level code execution, but the scenario requires local access, user interaction, and high complexity.
Executive priority
Treat this as a moderate endpoint hardening item. It is not remotely exploitable based on the source bundle, but SYSTEM privilege escalation can materially increase impact after an endpoint foothold.
Technical view
Multiple flaws in Zscaler Client Connector Installer and Uninstaller for Windows before 3.6 allowed binaries to be executed from a low-privileged path. The impact is local privilege escalation to SYSTEM. CVSS 3.1 is 6.7 with local attack vector, low privileges required, user interaction required, and high confidentiality, integrity, and availability impact.
Likely exposure
Organizations are most likely exposed where Windows endpoints use Zscaler Client Connector installer or uninstaller versions prior to 3.6. The source bundle does not identify non-Windows platforms as affected.
Exploitation context
The CVE is not listed as CISA KEV in the provided bundle, and no cited source states active exploitation. Practical exploitation requires local foothold, low privileges, user interaction, and high attack complexity.
Researcher notes
Focus validation on installer and uninstaller trust boundaries for Windows versions before 3.6. The available evidence is limited to the CVE description, CVSS data, and Zscaler release reference; avoid assuming affected builds or exploit availability beyond that.
Mitigation direction
- Inventory Windows Zscaler Client Connector versions across managed endpoints.
- Upgrade installations below version 3.6 according to Zscaler guidance.
- Remove or replace stale installer and uninstaller packages from endpoint-accessible paths.
- Restrict software install and uninstall workflows to trusted administrative channels.
- Monitor Zscaler advisories for any newer remediation guidance.
Validation and detection
- Confirm endpoint Client Connector versions are 3.6 or later.
- Check software distribution repositories for pre-3.6 installer or uninstaller packages.
- Review endpoint telemetry for suspicious privileged process creation during install or uninstall activity.
- Verify least-privilege controls around local software installation and removal.
- Document any legacy systems that cannot be upgraded immediately.
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-20: 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 lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-26736 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.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.