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CISA Adds One Known Exploited Vulnerability to Catalog

highknown exploitedpublic exploitCVE-2026-73570
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
CISA has added one new vulnerability to its Known Exploited Vulnerabilities (KEV) Catalog , based on evidence of active exploitation. CVE-2026-73570 Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability This type of vulnerability is a frequent attack vector for malicious cyber actors and poses significant risks to the federal enterprise. Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities, specifically those identified by Common Vulnerabilities and Exposures (CVEs) listed in CISA’s KEV Catalog on publicly exposed assets that grant total control of the asset post-exploitation, while deferring action for lower-risk vulnerabilities. BOD 26-04 further establishes basic expectations for when agencies must check whether threat actors compromised the system before the patch was applied. While BOD 26-04 applies only to FCEB agencies, CISA encourages all organizations to adopt risk-based vulnerability management and prioritize remediation of KEV Catalog vulnerabilities . CISA will continue to add vulnerabilities to the catalog that meet the specified criteria . Aware of an exploited vulnerability not currently listed in the KEV Catalog? Submit it for potential addition through CISA’s KEV Nomination Form . Potential KEV additions must have a CVE ID, evidence of exploitation, and clear mitigation guidance.

CSIRTS triage

What
OS command injection vulnerability allowing unauthenticated attackers to execute arbitrary operating system commands via specially crafted SMTP requests.
Who is affected
Unauthenticated attackers can exploit publicly exposed Zimbra Collaboration Suite deployments.
Urgency
Critical — actively exploited in the wild with total system compromise capability; federal agencies must prioritize remediation under BOD 26-04.
Action
Apply Zimbra security patch immediately; identify and patch all exposed Zimbra instances.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
CISA Cybersecurity Advisories (US · national-cert · site)
Severity
high
Published
2026-08-21
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://www.cisa.gov/news-events/alerts/2026/08/21/cisa-adds-one-known-exploited-vulnerability-catalog

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-73570coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

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