CVE-2020-11633Network attack vector

SYSTEM code execution via TLS stack overflow

Published Jul 15, 2021 · Updated Aug 4, 2024

Stack-based buffer overflow in Zscaler Client Connector for Windows before 2.1.2.74 allows remote attackers to execute SYSTEM code. The TLS connection path copies server-supplied data beyond a stack buffer when processing a misconfigured TLS server; the affected function and input field are undisclosed. Exploitation requires the Windows client to connect to such a server and results in arbitrary code execution with SYSTEM privileges.

CVSS severity9.8
Critical
EPSS probability1.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in Zscaler Client Connector for Windows before 2.1.2.74 allows remote attackers to execute SYSTEM code. The TLS connection path copies server-supplied data beyond a stack buffer when processing a misconfigured TLS server; the affected function and input field are undisclosed. Exploitation requires the Windows client to connect to such a server and results in arbitrary code execution with SYSTEM privileges.

The record

CVE
CVE-2020-11633
Published
Jul 15, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10.0NIST NVDAV:N/AC:L/Au:N/C:C/I:C/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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