Synacor Zimbra Collaboration Suite (ZCS) Command Execution Vulnerability

The postjournal service in Zimbra Collaboration (ZCS) before 8.8.15 Patch 46, 9 before 9.0.0 Patch 41, 10 before 10.0.9, and 10.1 before 10.1.1 sometimes allows unauthenticated users to execute commands.

CheckOps priority index

9.4/10 Patch within 24 h

Severity10.0

Probability10.0

Exploitation4/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 99.9% higher than 99.97% of CVEs

CVSS 3.1 10.0 AC:L/AV:N/A:H/C:H/I:H/PR:N/S:C

Exploited for 761 days 03 Oct 2024

CISA due date 24 Oct 2024 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 4 / 5

KEV catalog (CISA)03 Oct 2024
Exploited in EUVD (ENISA)03 Oct 2024
Used by ransomwareno
EPSS above 10 %99.9%
No account, over the networkyes

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Affected products

Zimbra Collaboration Suite (ZCS)

Weaknesses (CWE)

CWE-284

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

02 Oct 2024
Published
03 Oct 2024
Exploitation reported (ENISA)
03 Oct 2024
Added to the KEV catalog
24 Oct 2024
CISA remediation due date
25 Sept 2026
EPSS peak: 99.9%

References

Other exploited vulnerabilities from the same vendor

CVE-2026-73570Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability
8.1 · Actively exploited
CVE-2025-48700Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
4.3 · Background exploitation
CVE-2025-66376Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
5.9 · Background exploitation
CVE-2020-7796Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery Vulnerability
9.1 · Background exploitation
CVE-2025-68645Synacor Zimbra Collaboration Suite (ZCS) PHP Remote File Inclusion Vulnerability
7.4 · Background exploitation
CVE-2025-27915Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
3.5 · Background exploitation