Threats / Synacor / CVE-2023-37580
CVE-2023-37580
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Synacor Zimbra Collaboration Suite (ZCS) vulnerability
Synacor Zimbra Collaboration Suite contains a cross-site scripting vulnerability that could allow attackers to compromise data confidentiality and integrity through malicious scripts.
Verdict
Today item — known-exploited.
A reflected or stored XSS flaw in ZCS enables attackers to inject malicious scripts that execute in user browsers, potentially stealing session tokens, credentials, or sensitive email data. High EPSS score and active exploitation indicate immediate risk.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
7 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-07-27).
Probability (EPSS)
EPSS 0.59041 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Synacor, Zimbra Collaboration Suite (ZCS). Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious link or inject script into ZCS that executes when a user visits or interacts with the application.
Business
User credentials, email contents, and authentication tokens are exposed to unauthorized access, violating data confidentiality.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the XSS payload to modify email content, forwarding rules, or user settings visible to the victim.
Business
Email integrity is compromised; users cannot trust message authenticity or their account configurations.
3
Lateral reach — past segmentation narrative 3
Attacker
I redirect users to phishing pages or capture their session cookies via the injected script.
Business
Account takeover enables lateral movement within the organization and access to sensitive business communications.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05