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Vulnerability record · CVE-2021-35209 · published 2 July 2021

CVE-2021-35209: Zimbra collaboration server-side request forgery (ssrf) vulnerability

Zimbra · Collaboration

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).

9.8 CVSS 3.1 Critical EPSS 3.0% · top 13.2% CWE-918 · Server-side request forgery (SSRF)
9.8CVSS 3.1 base score, v2 7.5
3.0%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
10References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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).

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://blog.sonarsource.com/zimbra-webmail-compromise-via-email ExploitThird Party Advisory
https://wiki.zimbra.com/wiki/Security_Center Release NotesVendor Advisory
https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23 Release NotesVendor Advisory
https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16 Release NotesVendor Advisory
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories Vendor Advisory
https://blog.sonarsource.com/zimbra-webmail-compromise-via-email ExploitThird Party Advisory
https://wiki.zimbra.com/wiki/Security_Center Release NotesVendor Advisory
https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23 Release NotesVendor Advisory
https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16 Release NotesVendor Advisory
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

6.1CVE-2024-27443Zimbra webmail classic calendar invite XSS via crafted headerZimbra Collaboration 9.0 and 10.0 fail to properly validate the calendar header in the CalendarInvite feature of the classic webmail interface, allow…KEVEPSS 24%analysed9.8CVE-2023-29381Zimbra collaboration incorrect authorization vulnerabilityAn issue in Zimbra Collaboration (ZCS) v.8.8.15 and v.9.0 allows a remote attacker to escalate privileges and obtain sensitive information via the pa…EPSS 1.0%9.8CVE-2023-29382Zimbra collaboration code injection vulnerabilityAn issue in Zimbra Collaboration ZCS v.8.8.15 and v.9.0 allows an attacker to execute arbitrary code via the sfdc_preauth.jsp component.EPSS 1.0%9.8CVE-2022-32294Zimbra collaboration incorrect authorization vulnerabilityZimbra Collaboration Open Source 8.8.15 does not encrypt the initial-login randomly created password (from the "zmprove ca" command). It is visible i…EPSS 2.5%8.8CVE-2024-45518Zimbra collaboration server-side request forgery (ssrf) vulnerabilityAn issue was discovered in Zimbra Collaboration (ZCS) 10.1.x before 10.1.1, 10.0.x before 10.0.9, 9.0.0 before Patch 41, and 8.8.15 before Patch 46. …EPSS 21%8.8CVE-2023-34193Zimbra collaboration unrestricted file upload vulnerabilityFile Upload vulnerability in Zimbra ZCS 8.8.15 allows an authenticated privileged user to execute arbitrary code and obtain sensitive information via…EPSS 1.2%7.8CVE-2024-27442Zimbra collaboration improper privilege management vulnerabilityAn issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. The zmmailboxdmgr binary, a component of ZCS, is intended to be executed by the z…EPSS 0.35%7.8CVE-2023-24032Zimbra collaboration command injection vulnerabilityIn Zimbra Collaboration Suite through 9.0 and 8.8.15, an attacker (who has initial user access to a Zimbra server instance) can execute commands as r…EPSS 0.96%

Source: NIST National Vulnerability Database (record CVE-2021-35209), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.