Auth bypass in Synacor Zimbra Collaboration Suite

CVE-2026-73571

An authorization bypass vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.17 due to improper authorization validation in delegated email sending functionality. An authenticated attacker can send specially crafted SOAP requests to impersonate another user and send emails without possessing the required delegation or send-as permissions. This occurs in the SaveDraftRequest SOAP handler.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 3.1 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (15.7th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 15.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-73571: held from 0.002 to 0.003.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-73571?
CVE-2026-73571 is a low-severity vulnerability in Synacor Zimbra Collaboration Suite, classified under Incorrect Authorization. CVSS score: 3.1/10. Published 2026-08-13.
How severe is CVE-2026-73571?
Low severity. CVSS v3 base score is 3.1 out of 10.