CVE Intelligence
CISA KEV Medium Cross-site scripting

CVE-2025-48700 — Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability

An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15 and 9.0 and 10.0 and 10.1. A Cross-Site Scripting (XSS) vulnerability in the Zimbra Classic UI allows attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information. This issue arises from insufficient sanitization of HTML content, specifically involving crafted tag structures and attribute values that include an @import directive and other script injection vectors. The vulnerability is triggered when a user views a crafted e-mail message in the Classic UI, requiring no additional user interaction.

Published Jun 23, 2025 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: mitre

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Apr 20, 2026
How the score was calculated
  • Confirmed exploitation (CISA KEV)+35
  • EPSS 1.7% (30-day exploitation probability)+12
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Confirmed
CISA KEV, listed Apr 20, 2026
EPSS FIRST
1.71%
ahead of 77% of scored CVEs · Oct 14, 2026
Affects
Synacor
Zimbra Collaboration Suite
CVSS base
6.1
Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Active
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

CISA required action CISA

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

US federal deadline: Apr 23, 2026 — passed 175 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Synacor Zimbra Collaboration Suite).
  2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
  3. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  4. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  5. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  6. Search available logs for exploit probes matching the vulnerability class (cross-site scripting), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Synacor Zimbra Collaboration Suite version 9.0.0-p17version 9.0.0-p26version 9.0.0-p25version 9.0.0-p24.1version 9.0.0-p24version 9.0.0-p23version 9.0.0-p22version 9.0.0-p21
and 86 more version 9.0.0-p20version 9.0.0-p2version 9.0.0-p19version 9.0.0-p18version 9.0.0-p27version 9.0.0-p16version 9.0.0-p15version 9.0.0-p14version 9.0.0-p13version 9.0.0-p12version 9.0.0-p11version 9.0.0-p10version 9.0.0-p1version 9.0.0version 8.8.15-p9version 8.8.15-p8version 9.0.0-p37version 9.0.0-p9version 9.0.0-p8version 9.0.0-p7version 9.0.0-p6version 9.0.0-p5version 9.0.0-p42version 9.0.0-p41version 9.0.0-p40version 9.0.0-p4version 9.0.0-p39version 9.0.0-p38version 8.8.15-p7version 9.0.0-p36version 9.0.0-p35version 9.0.0-p34version 9.0.0-p33version 9.0.0-p32version 9.0.0-p31version 9.0.0-p30version 9.0.0-p3version 9.0.0-p29version 9.0.0-p28version 8.8.15-p18version 8.8.15-p28version 8.8.15-p27version 8.8.15-p26version 8.8.15-p25version 8.8.15-p24version 8.8.15-p23version 8.8.15-p22version 8.8.15-p21version 8.8.15-p20version 8.8.15-p2version 8.8.15-p19version 8.8.15-p29version 8.8.15-p17version 8.8.15-p16version 8.8.15-p15version 8.8.15-p14version 8.8.15-p13version 8.8.15-p12version 8.8.15-p11version 8.8.15-p10version 8.8.15-p1version 8.8.15≥ 10.1.0 and < 10.1.4version 8.8.15-p38version 8.8.15-p6version 8.8.15-p5version 8.8.15-p46version 8.8.15-p45version 8.8.15-p44version 8.8.15-p43version 8.8.15-p42version 8.8.15-p41version 8.8.15-p40version 8.8.15-p4version 8.8.15-p39≥ 10.0.0 and < 10.0.12version 8.8.15-p37version 8.8.15-p36version 8.8.15-p35version 8.8.15-p34version 8.8.15-p33version 8.8.15-p32version 8.8.15-p31.1version 8.8.15-p31version 8.8.15-p30version 8.8.15-p3
Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.1 CVSS 3.1 Medium 2.8 2.7 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
6.1 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
6.1 CVSS 3.1 Medium — — CISA-ADP via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N (score shown at the top: 134c704f-9b21-4f2e-91b3-4a467353bcc0)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-79 · Cross-site Scripting (XSS)

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed
Apr 20, 2026
Federal deadline
Apr 23, 2026
passed 175 day(s) ago
Ransomware use
Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

EPSS over time FIRST

Oct 12, 2026 → Oct 14, 2026 · 3 reading(s) · max 1.71%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Monitor CSP violation reports and script payloads in reflected parameters.
  • Hunt retroactively in logs from before Apr 20, 2026 (KEV listing): exploitation may have started earlier.
web/proxy/WAF logsnetwork IDS/IPSapplication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Affected products added · synacor/zimbra collaboration suite
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 6.1
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Added to CISA KEV (detected)
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Record created in this database
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Added to CISA KEV catalog
    Apr 19, 2026 · CISA
  • 2025
  • CVE published
    Jun 23, 2025 · mitre

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

6 on the record

Elsewhere on this site

Synacor
every CVE for this vendor
2026-04
what else CISA listed that month
Cross-site scripting
same class
CWE-79
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-73570 Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability KEV Aug 13, 2026
  • CVE-2026-33373 Cross-Site Request Forgery (CSRF) in Synacor Zimbra Collaboration Suite Mar 30, 2026
  • CVE-2026-33369 Improper Input Validation in Synacor Zimbra Collaboration Suite Mar 20, 2026
  • CVE-2026-33372 Cross-Site Request Forgery (CSRF) in Synacor Zimbra Collaboration Suite Mar 20, 2026
  • CVE-2026-33370 Cross-site Scripting (XSS) in Synacor Zimbra Collaboration Suite Mar 20, 2026
  • CVE-2026-33371 XML External Entity (XXE) in Synacor Zimbra Collaboration Suite Mar 20, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-48700 is "Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability", rated Medium. It affects Zimbra Collaboration Suite (Synacor); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 6.1 describes technical severity. EPSS 1.71% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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