Threats / Synacor / CVE-2023-37580
CVE-2023-37580
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
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.
CISA KEV Yes · 2023-07-274EPSS 0.46709 (verify live)5CVSS 6.1 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: partial3Exploit Public PoC / detection · nuclei template12
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 0.46709 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) · Affected: Synacor, Zimbra Collaboration Suite (ZCS). Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog the same day the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
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
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by mitreCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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