Medium severity · published Oct 8, 2026
CVE-2026-50055
Zimbra Collaboration Suite Sieve Notify Filter Action Bypasses Mail Forwarding Restriction via Variable Expansion
6.5
CVSS
0.4%
EPSS
No
On KEV
Description
A policy-enforcement flaw in Zimbra Collaboration Suite allows an authenticated user to bypass disabled mail forwarding by using a Sieve notify action to send copies of email content and headers to an arbitrary address.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 30% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CO
Collaboration · Zimbra
before 10.1.20 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-50055
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-50055
vendor-advisory
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
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