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Full vulnerability report · 2019
CVE-2019-9670High confidence

Synacor Zimbra Collaboration Suite (ZCS) Improper Restriction of XML External Entity Reference

Synacor · Zimbra Collaboration Suite (ZCS)

9.8CriticalCVSS 3.1
Recommended action
Patch now

CISA confirms exploitation in the wild and lists 2022-07-10 as the remediation due date.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, unchanged from published severity.unchanged

Evidence used

  • CISA confirms exploitation in the wild.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 99.99% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Synacor Zimbra Collaboration Suite (ZCS) and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2019-19036

CISA KEV mirrored by ENISA

mailboxd component in Synacor Zimbra Collaboration Suite 8.7.x before 8.7.11p10 has an XML External Entity injection (XXE) vulnerability, as demonstrated by Autodiscover/Autodiscover.xml.

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 10 Jan 2022. Evidence sources: cisa_kev.
ENISA score
9.8 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch now

CISA confirms exploitation in the wild and lists 2022-07-10 as the remediation due date.

Patch available
01

What, why and how

Synacor Zimbra Collaboration Suite (ZCS) contains an improper restriction of XML external entity (XXE) vulnerability in the mailboxd component.

What

Synacor Zimbra Collaboration Suite (ZCS) contains an improper restriction of XML external entity (XXE) vulnerability in the mailboxd component.

Why

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Synacor Zimbra Collaboration Suite (ZCS) contains an improper restriction of XML external entity (XXE) vulnerability in the mailboxd component.

Why

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2022-01-10.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Improper Restriction of XML External Entity Reference → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-611 ↗

CWE-611: Improper Restriction of XML External Entity Reference. The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-611CISA KEVPublic exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2019-19036Known-exploited evidence recorded

mailboxd component in Synacor Zimbra Collaboration Suite 8.7.x before 8.7.11p10 has an XML External Entity injection (XXE) vulnerability, as demonstrated by Autodiscover/Autodiscover.xml.

Official EUVD record ↗
Canadian Centre for Cyber Security · English · AL21-007APT Actors Target U.S. and Allied Networks - update 1

On 15 April 2021, the NSA, CISA, and FBI issued a Joint Cybersecurity Advisory [ 1 ], drawing attention to widespread scanning and exploitation of several vulnerabilities by APT actors. The advisory states that the APT actors are targeting vulnerable systems to obtain authentication credentials and enable further access within networks, including national security and government systems. Examples of recent activity include compromising SolarWinds Orion updates, targeting COVID-19 research facilities, and leveraging a VMWare vulnerability for authentication abuse. The Cybersecurity Advisory highlights the following vulnerabilities being exploited: CVE-2018-13379 Fortinet [ 2 ], [ 3 ] CVE-2019-9670 Zimbra [ 3 ] CVE-2019-11510 Pulse Secure [ 3 ], [ 4 ] CVE-2019-19781 Citrix [ 3 ] CVE-2020-4006 VMware [ 5 ] UPDATE 1 [ 6 ] CVE-2020-5902 F5 Big-IP CVE-2020-14882 Oracle WebLogic CVE-2021-21972 VMWare vSphere CVE-2019-1653 Cisco router CVE-2019-2725 Oracle WebLogic Server CVE-2019-7609 Kibana CVE-2021-26857 Exchange (SOAP payload) CVE-2021-26858 Exchange (Arbitrary files) CVE-2021-27065 Exchange (Arbitrary files) The Cyber Centre is highlighting this advisory, as it provides important information to system owners and operators responsible for defending their systems and networks from cyber threats. There are software updates and mitigations for these vulnerabilities. See past reporting by the Cyber Center and partners for more details. Should activity matching the content of this Alert be discovered, recipients are encouraged to contact the Cyber Centre by email ( contact@cyber.gc.ca ) or by telephone ( 1-833-CYBER-88 or 1-833-292-3788 ).

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2019-004926Synacor Zimbra Collaboration Suite における XML 外部エンティティの脆弱性

Synacor Zimbra Collaboration Suite には、XML 外部エンティティの脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
n/a
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 29 May 2019 · Last source change 21 Oct 2025, 23:45 UTC · CWE-611 · Improper Restriction of XML External Entity Reference

CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-01
European sourceENISA EUVD · EUVD-2019-19036
Product sourceCISA KEV
Remediation sourceCVE/CNA references
CWE sourceCISA ADP
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA known-exploited stateENISA EUVD now records this CVE in its known-exploited dataset.
    Before
    not listed in ENISA EUVD known-exploited dataset
    After
    listed in ENISA EUVD known-exploited dataset (EUVD-2019-19036)
    ENISA EUVD ↗
  2. ENISA EUVD mappingEUVD-2019-19036 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2019-19036"}
    ENISA EUVD ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    n/a: n/a · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    n/a · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CISA KEV ↗
  4. Affected versionsThe structured affected or fixed version information changed.
    Before
    n/a · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    n/a: n/a · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  5. Vendor guidanceAuthoritative vendor guidance changed: added patch: bugzilla.zimbra.com/show_bug.cgi?id=109129; added remediation: bugzilla.zimbra.com/show_bug.cgi?id=109129; 1 further additions.
    Before
    no authoritative guidance recorded
    After
    patch: bugzilla.zimbra.com/show_bug.cgi?id=109129 · remediation: bugzilla.zimbra.com/show_bug.cgi?id=109129 · vendor advisory: wiki.zimbra.com/Zimbra_Security_Advisories
    bugzilla.zimbra.com ↗
  6. Affected versionsThe structured affected or fixed version information changed.
    Before
    n/a · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    n/a · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  7. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    bugzilla.zimbra.com ↗
  8. Public exploit evidencePublic exploit evidence changed from Public exploit reference to Public exploit reference.
    Before
    Public exploit reference
    After
    Public exploit reference
    packetstormsecurity.com ↗
  9. CVSS scoreCVSS scoring authority changed from CISA ADP to NIST NVD; the displayed base score remained 9.8.
    Before
    9.8 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
    After
    9.8 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
    NIST NVD ↗
  10. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2019-19036↗CISA KEV record↗CVE authority or vendor reference↗Patch or update reference↗Public exploit reference↗Public exploit reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2019-9670 · cve.blacktree.nl