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Client ConnectorApplication · Zscaler

CVE-2021-26738

HIGH · 7.8 CVSS v3.1 Published 2023-10-23
Fix available
A fix is available. Upgrade to 3.7 or later.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Zscaler Client Connector for macOS prior to 3.7 had an unquoted search path vulnerability via the PATH variable. A local adversary may be able to execute code with root privileges.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The vulnerability is an unquoted search path issue in Zscaler Client Connector for macOS where the PATH environment variable is not properly validated or quoted, allowing a local attacker to place a malicious executable earlier in the PATH to be invoked instead of the intended binary. Since the application runs with elevated (root) privileges, this enables local privilege escalation.

MitigationUpgrade Zscaler Client Connector for macOS to version 3.7 or later to remediate this vulnerability.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Client ConnectorApplication
Affected:< 3.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if Zscaler Client Connector is installed
    Open Terminal and run: ls /Applications/ | grep -i zscaler OR ls /Applications/ | grep -i "Zscaler Client"
    Affected if The application directory does not exist in /Applications - not affected
  2. Identify the installed version
    Run: defaults read /Applications/Zscaler\ Client\ Connector.app/Contents/Info CFBundleShortVersionString
    Affected if Version returned is less than 3.7 (e.g., 3.6.x, 3.5.x, etc.) - likely affected
  3. Check for the Zscaler service daemon
    Run: ls /Library/Application\ Support/Zscaler/ to locate the service components that run with elevated privileges
    Affected if Service daemon files exist in this directory and version is below 3.7 - affected if unquoted PATH handling is present in launch scripts or service wrappers
  4. Inspect launchd configuration for unquoted PATH usage
    Run: sudo launchctl list | grep -i zscaler to find running Zscaler services, then examine the plist for how it invokes binaries
    Affected if A launchd service for Zscaler exists and uses unquoted binary paths - vulnerable to PATH hijacking
  5. Verify if the application runs with root privileges
    Check the service configuration: ls -la /Library/Application\ Support/Zscaler/ and look for executable permissions indicating root-level execution
    Affected if The service runs as root (user ID 0) and uses unquoted PATH to invoke binaries - vulnerable to local privilege escalation

A user is affected if Zscaler Client Connector version is below 3.7 AND the service runs with elevated privileges using an unquoted PATH to locate executables.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.7 or later
Fixed in 3.7
Interim mitigation

Upgrade Zscaler Client Connector for macOS to version 3.7 or later to remediate this vulnerability.

Recommended fix High confidence

3.7

  1. Download Zscaler Client Connector version 3.7 or later from the official Zscaler support portal at help.zscaler.com
  2. Install the updated Client Connector version following standard installation procedures
  3. Verify the installed version is 3.7 or higher to confirm the vulnerability is remediated

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Client Connector Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-26738 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data