{"id":"CVE-2021-35209","aliases":["EUVD-2021-21853","GHSA-wv5j-j74p-fv28"],"status":"published","title":"An issue was discovered in ProxyServlet.java in the /proxy servlet in Zimbra Collaboration Suite...","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).","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.02995,"percentile":0.87453,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-601","CWE-918"],"published":"2021-07-02T18:54:43Z","modified":"2026-10-24T10:30:55Z","products":[{"vendor":"zimbra","product":"collaboration"}],"references":[{"url":"https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories","tags":["x_refsource_MISC","x_transferred","Vendor Advisory","advisory"]},{"url":"https://wiki.zimbra.com/wiki/Security_Center","tags":["x_refsource_MISC","x_transferred","Release Notes","Vendor Advisory","advisory"]},{"url":"https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16","tags":["x_refsource_MISC","x_transferred","Release Notes","Vendor Advisory","advisory"]},{"url":"https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23","tags":["x_refsource_MISC","x_transferred","Release Notes","Vendor Advisory","advisory"]},{"url":"https://blog.sonarsource.com/zimbra-webmail-compromise-via-email","tags":["x_refsource_MISC","x_transferred","Exploit","Third Party Advisory","evidence"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-35209"},{"url":"https://github.com/advisories/GHSA-wv5j-j74p-fv28"}],"sources":{"cve":[{"id":"CVE-2021-35209","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).","status":"published","published":"2021-07-02T18:54:43Z","modified":"2024-08-04T00:33:51.186Z","updated_at":"2026-11-02T14:33:09.864034Z"}],"euvd":[{"id":"EUVD-2021-21853","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).","status":"published","published":"2021-07-02T18:54:43Z","modified":"2024-08-04T00:33:51Z","updated_at":"2026-11-03T03:24:30.986651Z"}],"ghsa":[{"id":"GHSA-wv5j-j74p-fv28","title":"An issue was discovered in ProxyServlet.java in the /proxy servlet in Zimbra Collaboration Suite...","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).","status":"published","published":"2022-05-24T19:06:48Z","modified":"2023-01-30T05:00:35Z","cwes":["CWE-601","CWE-918"],"updated_at":"2026-11-02T14:46:14.069279Z"}],"nvd":[{"id":"CVE-2021-35209","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).","status":"published","published":"2021-07-02T19:15:08.46Z","modified":"2026-06-17T03:57:18.203Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"cwes":["CWE-918"],"updated_at":"2026-11-02T14:06:55.259633Z"}],"osv":[{"id":"CVE-2021-35209","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).","status":"published","published":"2021-07-02T19:15:08.46Z","modified":"2026-10-24T10:30:55.997920077Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:44:20.13324Z"}]}}