CVE-2023-28807

Security-control bypass via CONNECT-to-SNI mismatch

Published Jan 31, 2024 · Updated Jun 17, 2025

Improper certificate validation in Zscaler Internet Access before 6.2r.290 allows attackers to bypass network security controls. The domain-fronting detector fails to enforce consistency between the HTTP CONNECT host and TLS ClientHello SNI, allowing dissimilar names to pass as legitimate traffic. Reachability requires control of traffic routed through ZIA and the affected domain-fronting policy path; the result is concealed communications rather than service interruption.

CVSS severity5.1
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Zscaler Internet Access before 6.2r.290 allows attackers to bypass network security controls. The domain-fronting detector fails to enforce consistency between the HTTP CONNECT host and TLS ClientHello SNI, allowing dissimilar names to pass as legitimate traffic. Reachability requires control of traffic routed through ZIA and the affected domain-fronting policy path; the result is concealed communications rather than service interruption.

The record

CVE
CVE-2023-28807
Published
Jan 31, 2024
Updated
Jun 17, 2025
Vendor
Zscaler
Product
Zscaler Internet Access
Classifications
CWE-295, CAPEC-554, T1090.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 31, 2024CVE publishedPublication date reported by the CVE source.
  2. Jun 17, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <6.2r.290

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Zscaler · Zscaler Internet Accessversion=0 <6.2r.290

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.1Zscaler, Inc.CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
CAPEC-554Functionality Bypass
T1090.004Proxy: Domain Fronting

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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