Read the docs
TI-2026-69621 Aliases CVE-2026-50055GHSA-p88h-r6ph-r7j6

Sieve notify action bypasses mail forwarding restriction in Zimbra

Priority LOW 29CWE-863Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-863.

Summary

Zimbra Collaboration Suite from 0 before 10.1.20 contains an incorrect authorization flaw (CWE-863) in its Sieve notify filter action. An authenticated user can bypass disabled mail forwarding by using a Sieve notify action with variable expansion to send copies of email content and headers to an arbitrary address.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00363 30th percentileScored 2026-11-07
Fix Fixed Zimbra Collaboration Suite (Zimbra): 10.1.20

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ZimbraZimbra Collaboration Suitebefore 10.1.2010.1.20Patch availableCNA
  • Zimbra Collaboration Suite VendorZimbra Affected before 10.1.20 Fixed in 10.1.20 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*——Synacor
  • cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:* Versions — — ·Synacor

Remediation

Upgrade Zimbra Collaboration Suite to version 10.1.20 or later.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • Fix · CNA Zimbra Collaboration Suite (Zimbra) Fixed in 10.1.20

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Zimbra Collaboration Suite 10.1.20

    3 records Highest priority Priority LOW 3 LOW

    Other records, highest priority first

    • TI-2026-69620 Zimbra Collaboration Suite flaw lets accounts grant mailbox accessPriority LOW 30
    • TI-2026-69618 Zimbra Collaboration Suite EWS authorization bypass exposes mailboxesPriority LOW 29
    Show all 3 records →

Timeline

  1. 2026-10-08 Threatist record created from CVE-2026-50055
  2. 2026-10-08 CISA SSVC decision points changed
  3. 2026-10-09 Alias added: GHSA-p88h-r6ph-r7j6
  4. 2026-10-09 Priority changed: MEDIUM → LOW

References

Advisory 1

  • TI-2026-51660 OS command injection in Zimbra Collaboration KEVCVSS 3.1HIGH 8.9
  • TI-2025-40820 Cross-site scripting in Zimbra Collaboration KEVCVSS 3.1HIGH 7.2
  • TI-2024-18266 An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. KEVCVSS 3.1MEDIUM 6.1
  • TI-2024-30553 An issue was discovered in Zimbra Collaboration (ZCS) 10.1.x before 10.1.1, 10.0.x before… CVSS 3.1HIGH 8.8
  • TI-2022-13998 Zimbra Collaboration Open Source 8.8.15 does not encrypt the initial-login randomly… CVSS 3.1CRITICAL 9.8
  • TI-2026-63080 Path traversal in Zimbra Collaboration Suite CVSS 3.1CRITICAL 9.8
See all 94 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences