Threats / Synacor / CVE-2019-9621
CVE-2019-9621
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Synacor Zimbra Collaboration Suite (ZCS) vulnerability
Synacor Zimbra Collaboration Suite contains a server-side request forgery vulnerability in ProxyServlet, allowing attackers to make unauthorized requests from the affected server.
Verdict
Today item — known-exploited.
An SSRF flaw in ZCS ProxyServlet enables attackers to forge requests originating from the server, potentially accessing internal resources, bypassing network controls, or pivoting to backend systems. Active exploitation observed.
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
4 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 2025-07-07).
Probability (EPSS)
EPSS 0.80906 — 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-918 Server-Side Request Forgery (SSRF), CWE-807 CWE-807.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 request to ProxyServlet that causes the server to make an internal request on my behalf.
Business
Internal network resources become accessible to external attackers without authentication.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the server's trusted network position to access backend services, databases, or metadata endpoints that reject external connections.
Business
Sensitive internal data and system configurations are exposed to compromise.
3
Lateral reach — past segmentation narrative 3
Attacker
I enumerate and attack internal services by leveraging the compromised server as a proxy for reconnaissance and exploitation.
Business
Infrastructure security perimeter is effectively bypassed, enabling lateral movement and further system compromise.
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