CyberSecBulletin
CVE-2026-73570Exploited in the wildNVD status: Analyzed

Zimbra Collaboration Suite (ZCS) OS Command Injection

Published Updated By the CyberSecBulletin desk

CVE-2026-73570 is a high-severity improper neutralization of special elements used in an OS command vulnerability in Collaboration from Zimbra, with a CVSS 3.1 base score of 8.9 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 10.1.20 as the first without the flaw, so updating Collaboration to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on August 21, 2026, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Collaboration to 10.1.20 or a later version.
  2. Update Zimbra Collaboration Suite to 10.1.20 or a later version.
  3. CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
  4. Read the advisory on wiki.zimbra.com for workarounds and exact fixed builds.
  5. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
ZimbraCollaborationbefore 10.1.2010.1.20
SynacorZimbra Collaboration Suitebefore 10.1.2010.1.20

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
LowPerformance or availability is reduced.

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L. Scored by CNA (mitre.org).

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements used in an OS Command

The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.

How developers prevent this class of flaw

  • If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  4. Record last changed materially (score, affected products, status or references).
  5. Deadline for US federal agencies to remediate, set by CISA.

References

Patches and release notes

Other vulnerabilities in Collaboration

All Collaboration vulnerabilities

Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities

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