Threats / Synacor / CVE-2019-9670
CVE-2019-9670
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Synacor Zimbra Collaboration Suite (ZCS) vulnerability
Synacor Zimbra Collaboration Suite mailboxd component contains an XML external entity (XXE) vulnerability allowing improper XML processing.
Verdict
Today item — known-exploited.
An XXE flaw in ZCS mailboxd enables attackers to read arbitrary files, perform SSRF attacks, or cause denial of service through maliciously crafted XML input. Active exploitation in the wild with high exploitability.
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
916 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 2022-01-10).
Probability (EPSS)
EPSS 0.99986 — 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-611 XML External Entity (XXE) — 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 malicious XML with external entity declarations targeting the ZCS mailboxd service.
Business
Attackers gain unauthorized access to sensitive files and system information stored on mail servers.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I leverage XXE to perform server-side request forgery against internal network resources.
Business
Internal systems and services become exposed to lateral movement and reconnaissance by external threat actors.
3
Lateral reach — past segmentation narrative 3
Attacker
I submit billion laughs or external entity expansion payloads to exhaust server resources.
Business
Mail service availability degrades, disrupting business communications and user productivity.
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