What’s Vulnerable › Vulnerabilities

CVE-2026-50055: Zimbra Collaboration Suite Sieve Notify Filter Action Bypasses Mail Forwarding Restriction via Variable Expansion

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-08 · updated 2026-10-08
• Weakness: CWE-863

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.

Affected products

• Zimbra Collaboration: before 10.1.20 — fixed in 10.1.20

How to fix

Upgrade to a fixed version: Zimbra Collaboration 10.1.20. Check the vendor advisory for mitigations.

In the news

• From One Account to Every Mailbox: Breaking Zimbra's Identity Boundaries (Part 1)

References

• https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories

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