9.1

CVE-2026-59564: zscaler client_connector Missing Critical Step in Authentication

CVSS: 9.1v3.1CriticalAwaiting analysis
Published 24-08-2026Last modified 25-08-2026
Open JSON

Vulnerability summary

CVE-2026-59564 is a critical (CVSS 9.1) Missing Critical Step in Authentication vulnerability in zscaler client_connector. EPSS estimates a 0.53% chance of exploitation in the next 30 days, higher than 43.6% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.1/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.53%
0%100%
Low · +0.23 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 24-08-2026
    PublishedVulnerability first disclosed.
  2. 25-08-2026
    Last modifiedVulnerability information updated.

Description

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

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.53%

Chance of exploitation in the next 30 days

Percentile

44%

Versus all other CVEs

30-day change

+0.23 pp

From 0.30% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.53%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Zscaler1 product
  • client_connector< 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 | < Android: 4.2 | < ChromeOS: 4.2 | < Linux: 3.7.2.64, 4.2.1.64

1 vendor · 1 product

References

1 links