CVE-2021-35209

highpriority · track · 40EPSS 0.030 · 87 %ileEUUS

grimoire priorityP2 · Scheduled

Exploitable?

—

no known exploitation

Likely / severe?

3.00% (87th) EPSS

CVSS 7.5 · high

Is it mine?

4 products

Check your exposure

Who says so?

3 sources

cnnvd · enisa_euvd · nvd

EPSS · scored 2026-10-28

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

Technical severity, 0–10. One row per scoring source.

9.8

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 7.5–9.8

v2.07.5highAV:N/AC:L/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 10 · impact 6.4

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 5.9

v3.19criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-918USprimary

affected products (4)

Products and version ranges known to be affected.

n/a n/a≤ n/aenisa_euvdEU
zimbra collaboration8.8 → 8.8.15nvdUScpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*
zimbra collaboration= 8.8.15nvdUScpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*
zimbra collaboration= 9.0.0nvdUScpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd NVD CVE.org MITRE

published 2021-07-02modified 2026-06-17

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+4181 more

references (17)

External citations — patches, advisories, analysis.

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