Zimbra Denial of Service Vulnerability

CSIRTS triage

What

A denial of service vulnerability has been discovered in Zimbra.

Who is affected

Deployments of Zimbra are affected.

Urgency

Remediation is urgent due to the potential for service disruption.

Action

Apply the latest security updates for Zimbra.

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

Details

Source

HKCERT Security Bulletins (HK · national-cert · site)

Severity

unknown

Published

2026-06-22

Exploitation

Not in CISA KEV at last sync

Original advisory: https://www.hkcert.org/security-bulletin/zimbra-denial-of-service-vulnerability_20260622

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.

• Elevated exploitation riskCVE-2026-4997511.5% 30-day exploitation probability — well above the norm. Schedule remediation this cycle. Riskier than 96% of all scored CVEs.

Referenced CVEs

Same CVEs, other sources

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

• high[UPDATE] [high] Apache HTTP Server: Multiple vulnerabilitiescert-bund
• high[UPDATE] [high] HTTP/2 implementations: Vulnerability allows denial of servicecert-bund
• highCVE-2026-49975: Apache HTTP Server: mod_http2 denial of servicemsrc

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