Vulnerability report

Active exploitation observed Confirmed confidence In CISA KEV

CVE-2026-73570

Collaboration Remote Code Execution

Zimbra / Collaboration · affected before 10.1.20

Watch CVE-2026-73570 Browse KEV feed
Severity
CVSS 8.9 · High
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
71.7%
First observed
24 Aug 2026
Last observed
01 Oct 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-73570 is an unauthenticated vulnerability affecting Zimbra Collaboration. A remote code execution vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.20 when the optional zimbra-snmp package is...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence. Listed in CISA KEV. Also confirmed by third-party sources.

Who is affected?

Zimbra / Collaboration affected before 10.1.20.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Collaboration Remote Code Execution

A remote code execution vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.20 when the optional zimbra-snmp package is installed and SNMP notifications are enabled.

Due to improper sanitization of untrusted input during SNMP notification processing, an unauthenticated attacker can send specially crafted SMTP requests that may result in execution of arbitrary operating system commands as the Zimbra user.

Zimbra Affected
Collaboration
Before 10.1.20
Published
13 Aug 2026
Exploitation Reported
20 Aug 2026
Attack vector
Remote
Complexity
High
Privileges
None
User interaction
None

Tags

cisa nuclei_scanner

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

The Hacker News

Recorded 20 Aug 2026

A trusted third party reported exploitation.

Active exploitation observed

Previdian sensor

First observed 24 Aug 2026

Previdian first observed exploitation attempts targeting this vulnerability in our honeypot sensors.

Proof of concept available

GitHub

Recorded 21 Aug 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CERT Polska First 2026-08-17 09:01 UTC
The Hacker News 2026-08-20 13:24 UTC
CISA 2026-08-21 16:42 UTC
CVE 2026-08-21 17:40 UTC
The Shadowserver 2026-08-23 00:00 UTC
Previdian Sensors 2026-08-24 12:15 UTC
Microsoft Threat Intelligence 2026-09-30 18:21 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Previdian sensors recorded exploitation attempts targeting this vulnerability. The cards and chart show volume, unique attackers, and daily activity.

43

Attempts observed

4

Unique attacker IPs

4

Attacker countries

CN · SA · TL · US

1

Sensors observed

CVE-2026-73570 exploitation attempts over the last 51 days

Daily events observed by Previdian sensors

Updated 12 Oct 2026

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41
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0
0
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1
0
0
0
0
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0
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23 Aug 3 Sep 14 Sep 25 Sep 12 Oct

First observed 24 Aug 2026 · Last observed 01 Oct 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
1
1
3

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

Previdian virtual patch guidance is available for this CVE.

AWS WAF Cloudflare ModSecurity

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

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Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/network/cves/2026/CVE-2026-73570.yaml 27 Aug 2026

Virtual Patch Detail

Compensating WAF rules for this CVE.

Available

Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to Previdian Enterprise users.

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Risk and context

Severity, weaknesses, and research context

CVSS v3.1

8.9 High

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L

EPSS

71.7%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') CWE-78

Recent mention · TheRegister

Microsoft catches hackers exploiting Zimbra bug before disclosure

Attackers were probing the mail server flaw weeks before it had a CVE to its name

Read full advisory

All Mentions

Recent mention · TheRegister

Microsoft catches hackers exploiting Zimbra bug before disclosure

TheRegister · 01 Oct 2026

Attackers were probing the mail server flaw weeks before it had a CVE to its name

Recent mention · Microsoft Threat Intelligence

Unauthenticated command injection on internet-facing mail servers: tracking CVE-2026-73570

Microsoft Threat Intelligence · 30 Sep 2026

Microsoft Threat Intelligence examines CVE-2026-73570 exploitation in Zimbra, including observed attack paths, detection opportunities, and mitigation guidance. The post Unauthenticated command injection on internet-facing mail servers: tracking CVE-2026-73570 appeared first on Microsoft Security Blog.

Recent mention · The Hacker News

Attackers Exploit Zimbra Flaw to Deploy Web Shells and Harvest Authentication Secrets

The Hacker News · 30 Sep 2026

Ravie LakshmananSep 30, 2026Vulnerability / Email Security Threat actors have weaponized a now-patched security flaw in Zimbra Collaboration Suite (ZCS) to deploy web shells and access mailbox data, according to findings from the Microsoft Security Research team. The attack exploits CVE-2026-73570 (CVSS score: 8.9), an unauthenticated operating system command injection flaw that can lead to remote code execution when Simple Network Management Protocol (SNMP) notifications are enabled and the optional zimbra-snmp package is installed. Exploitation of CVE-2026-73570 can be triggered by a...

Recent mention · Rapid7

When Business Email Compromise Starts Rewriting Reality

Rapid7 · 24 Sep 2026

Business Email Compromise (BEC) operates on a familiar playbook. Threat actors breach a mailbox, silently monitor operations, map approval chains, and ultimately exploit that access to divert funds or exfiltrate sensitive assets.This dynamic is central to our analysis as we kick off a series around Rapid7's collaborative research with Zimbra; upcoming installments will explore technical details and broader findings based within the Zimbra Collaboration Suite. Our investigation disrupted the traditional BEC model in unexpected ways. We uncovered over 50 vulnerabilities, and found that...

Recent mention · RecordedFuture

August 2026 CVE Landscape

RecordedFuture · 08 Sep 2026

In August 2026, Insikt Group® identified 73 high-impact vulnerabilities that should be prioritized for remediation, 43 of which had a Very Critical Recorded Future Risk Score. This represents a 14% decrease from last month.

Recent mention · Dark Reading

Exploited Zimbra Flaw Highlights Shrinking Window to Patch

Dark Reading · 24 Aug 2026

CISA has issued a three-day deadline for agencies to patch a Zimbra security vulnerability, CVE-2026-73570, which allows full takeover of a user's communications.

Recent mention · The Hacker News

Attackers Exploit Zimbra SNMP Flaw for Unauthenticated Remote Code Execution

The Hacker News · 20 Aug 2026

A now-patched security flaw impacting Zimbra Collaboration (ZCS) has come under active exploitation in the wild, according to the Polish Computer Emergency Response Team (CERT Polska). The vulnerability in question is CVE-2026-73570 (CVSS score: 8.9), which refers to a case of command injection that can lead to remote code execution. "A remote code execution vulnerability exists in Zimbra

Recent mention · CERT Polska

Aktywnie wykorzystywana podatność w Zimbra Collaboration Suite

CERT Polska · 17 Aug 2026

Zespół CERT Polska informuje o aktywnie wykorzystywanej podatności typu OS Command Injection w Zimbra Collaboration Suite.Podatność, oznaczona jako CVE-2026-73570, pozwala nieuwierzytelnionemu atakującemu na wykonanie dowolnych komend powłoki systemowej z uprawnieniami użytkownika zimbra. Podatność dotyczy instancji posiadających włączoną usługę pułapek SNMP (ang. SNMP trap) za pomocą parametru snmp_notify oraz uruchomioną usługę swatchdog (domyślnie włączona).Podatność została wyeliminowana w wersji 10.1.20.Zalecamy niezwłoczną weryfikację wersji wykorzystywanego przez Państwa...

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

0xBlackash/CVE-2026-73570

github · Created 2026-09-30 21:13:26 UTC · 0 stars · AI assessment 90%

CVE-2026-73570

juanpoch/CVE-2026-73570

github · Created 2026-09-05 22:48:51 UTC · 0 stars · AI assessment 90%

Zimbra Collaboration Suite RCE — SMTP log poisoning → swatchdog → OS Command Injection (CVSS 8.9, CISA KEV)

byt3l0rd/CVE-2026-73570

github · Created 2026-09-02 17:33:44 UTC · 0 stars · AI assessment 85%

gabrielunknown/CVE-2026-73570

github · Created 2026-08-26 03:30:14 UTC · 0 stars · AI assessment 90%

Zimbra SNMP Notification OS Command Injection — Unauthenticated RCE via SMTP exploit (Poc)

jishino567/CVE-2026-73570

github · Created 2026-08-25 10:25:53 UTC · 0 stars · AI assessment 90%

PoC for CVE-2026-73570 (Zimbra SMTP Command Injection)

BiuTrap/CVE-2026-73570

github · Created 2026-08-24 11:55:28 UTC · 0 stars · AI assessment 85%

CVE-2026-73570 PoC

Zimbra Collaboration unauthenticated RCE via Swatchdog/SNMP log-injection command injection (swatchrc dosnmp Perl backtick)

pruva · Created 2026-08-23 15:38:38 UTC

Severity: HIGH | CVE: CVE-2026-73570 | Package: Zimbra Collaboration (ZCS)

HORKimhab/CVE-2026-73570

github · Created 2026-08-21 03:18:23 UTC · 0 stars · AI assessment 90%

CVE-2026-73570

Zimbra Collaboration Suite < 10.1.20 - OS Command Injection

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 13:02 UTC

    Virtual patch available

    Compensating WAF rule available to block exploitation

  2. 18:21 UTC

    KEV confirmed by Microsoft Threat Intelligence

    Exploitation attested by an external source

  3. 04:31 UTC

    Nuclei template available

    Scanner coverage available

  4. 12:12 UTC

    Indicators of compromise added (4)

    Indicators of compromise recorded

  5. 12:12 UTC

    Observed by Previdian sensors

    Evidence-backed exploitation signal

  6. 00:00 UTC

    KEV confirmed by The Shadowserver

    Exploitation attested by an external source

  7. 17:40 UTC

    KEV confirmed by CVE

    Exploitation attested by an external source

  8. 16:42 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  9. 03:18 UTC

    Public PoC available

    Public proof-of-concept code published

  10. 13:24 UTC

    KEV confirmed by The Hacker News

    Exploitation attested by an external source

  11. 09:01 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  12. 15:19 UTC

    CVE published

    Vulnerability disclosed publicly

  13. 21:44 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

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Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
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GET /api/v2/pro/kevs/CVE-2026-73570

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2026-73570",
  "confidence": "Confirmed",
  "cvss_score": 8.9,
  "cvss_estimated": false,
  "epss_score": 0.71663,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 43, "sensors": 1 }
}