CVE-2021-35209
9.8
CRITICAL · CVSS 3.1 · EPSS 3% (pctl 87)
In your normal cycle
Critical by CVSS (9.8), but no sign of active exploitation.
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).
Scoring
| CVSS | 9.8 (CRITICAL, v3.1) |
|---|---|
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| EPSS | 3% — more likely to be exploited than 87% of all CVEs |
| Weakness | CWE-918 |
| On CISA KEV | no |
| Public exploit | none known |
| Published | 2021-07-02 |
| Last modified | 2026-06-17 |
Affected (1)
| Vendor | Product |
|---|---|
| zimbra | collaboration |
References
- https://blog.sonarsource.com/zimbra-webmail-compromise-via-email
- https://wiki.zimbra.com/wiki/Security_Center
- https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
- https://blog.sonarsource.com/zimbra-webmail-compromise-via-email
- https://wiki.zimbra.com/wiki/Security_Center
- https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
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