# CVE-2026-59564 — Zscaler Client Connector

> As of 2026-08-25, CVE-2026-59564 is a CRITICAL-severity vulnerability in Zscaler Client Connector, CVSS v3.1 9.1, EPSS 0.5% (42.9th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-59564, most recently “Multiple Zscaler Client Connector Flaws Enable Remote Code Execution (CVE-2026-59568)”.

**Last updated:** 2026-08-25

## What is CVE-2026-59564?

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

The record classifies CVE-2026-59564 under weakness class [CWE-304](https://cwe.mitre.org/data/definitions/304.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 65 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 9.1 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **EPSS (FIRST):** 0.5% probability of exploitation in the next 30 days, higher than 42.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 6.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-24, last modified 2026-08-25

## Is CVE-2026-59564 being exploited?

It currently carries a trending score of 34 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Zscaler](https://intel.threadlinqs.com/vendors/zscaler): Client Connector

## How to fix CVE-2026-59564

No vendor patch reference has been recorded for CVE-2026-59564 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-59564

1 tracked threat in the Threadlinqs corpus references CVE-2026-59564, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Multiple Zscaler Client Connector Flaws Enable Remote Code Execution (CVE-2026-59568)](https://intel.threadlinqs.com/threat/TL-2026-2139) — CRITICAL · 2026-08-25

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10.

**Other references**

- [help.zscaler.com](https://help.zscaler.com/zscaler-client-connector/client-connector-app-release-summary-2026)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-59564
Full detection coverage and IOCs for threats exploiting CVE-2026-59564 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp