# CVE-2026-59565: Zscaler Client Connector buffer overflow denial-of-service

Source: https://junglewise.ai/threats/cve-2026-59565-zscaler-client-connector-buffer-overflow-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-24. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-59565 · Severity: high · CVSS 8.8 · Published 2026-08-24

Zscaler Client Connector is a network security client deployed on Windows endpoints to enforce security policies. A remotely exploitable buffer overflow in this client can be leveraged to crash the application and the Windows kernel, disrupting endpoint security protections and potentially requiring manual intervention to restore service.

Technologies: [Zscaler Client Connector](https://junglewise.ai/threats/technologies/client-connector). Vendors: [Zscaler](https://junglewise.ai/threats/vendors/zscaler).

## Quick answers

**Is CVE-2026-59565 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-59565 being exploited in the wild.

**How severe is CVE-2026-59565?** High severity, with a CVSS score of 8.8, published 24 August 2026.

**Which products and versions are affected?** Zscaler Client Connector <UNKNOWN>.

**Is there a fix for CVE-2026-59565?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-59565 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-59565?** Check whether you run Zscaler Client Connector at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a buffer overflow flaw in Zscaler Client Connector for Windows that can be exploited remotely to trigger both local and kernel denial-of-service conditions. The exact vulnerable component and attack vector are not detailed in the available references, but the remotely exploitable nature suggests the flaw may be reachable via network traffic processed by the client. Successful exploitation results in application crash or kernel-level DoS, disabling the client's security enforcement. Patches are available from Zscaler; affected users should upgrade to patched versions.

## Affected products

- Zscaler Client Connector <UNKNOWN>

## Timeline

- 2026-08-24: disclosed

## References

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

## Related threats

- [Zscaler Client Connector peer app access control bypass](https://junglewise.ai/threats/cve-2026-59570-zscaler-client-connector-peer-app-access-control-bypass)
- [Zscaler Client Connector improper input validation on Android and ChromeOS](https://junglewise.ai/threats/cve-2026-59569-zscaler-client-connector-improper-input-validation-on-android-and)
- [Zscaler Client Connector race condition in ZPA tunnel handler](https://junglewise.ai/threats/cve-2026-25687-zscaler-client-connector-race-condition-in-zpa-tunnel-handler)
- [Zscaler Client Connector remote code execution](https://junglewise.ai/threats/cve-2026-59568-zscaler-client-connector-remote-code-execution)
- [Zscaler Client Connector local privilege escalation](https://junglewise.ai/threats/cve-2026-59567-zscaler-client-connector-local-privilege-escalation)