CyberSecBulletin
CVE-2026-59564NVD status: Awaiting Analysis

Client Connector: Missing Critical Step in Authentication

Published Updated By the CyberSecBulletin desk

CVE-2026-59564 is a critical-severity missing critical step in authentication vulnerability in Client Connector from Zscaler, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions Windows: 4.6.0.457, 4.7.0.317, 4.8.0.232, 4.9.0.372, MacOS: 4.5.2.312, 4.7.0.292, 4.8.0.191, iOS: 4.5.1 as the first without the flaw, so updating Client Connector to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.53% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Client Connector to Windows: 4.6.0.457, 4.7.0.317, 4.8.0.232, 4.9.0.372 or MacOS: 4.5.2.312, 4.7.0.292, 4.8.0.191 or iOS: 4.5.1 or Android: 4.2, whichever matches your release line, or a later version.
  2. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
ZscalerClient Connectorbefore Windows: 4.6.0.457, 4.7.0.317, 4.8.0.232, 4.9.0.372; before MacOS: 4.5.2.312, 4.7.0.292, 4.8.0.191; before iOS: 4.5.1; before Android: 4.2; before ChromeOS: 4.2; before Linux: 3.7.2.64, 4.2.1.64Windows: 4.6.0.457, 4.7.0.317, 4.8.0.232, 4.9.0.372, MacOS: 4.5.2.312, 4.7.0.292, 4.8.0.191, iOS: 4.5.1, Android: 4.2, ChromeOS: 4.2, Linux: 3.7.2.64, 4.2.1.64

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by CNA (zscaler.com).

Official description

An authentication bypass issue exists in communications between affected versions of the Zscaler Client Connector and the Zscaler Client Connector Portal.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Missing Critical Step in Authentication

The product implements an authentication technique, but it skips a step that weakens the technique.

More Missing Critical Step in Authentication vulnerabilities (CWE-304)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Client Connector

All Client Connector vulnerabilities

Recent Missing Critical Step in Authentication vulnerabilities

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