CVE-2026-93640

HIGH CVSS 7.8 PoC Available
Published: 2026-10-23
Modified: 2026-10-24
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AI Threat Summary

CVE-2026-93640 is a high-severity vulnerability with a CVSS score of 7.8 affecting the target software. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

A local privilege escalation vulnerability in the optional dnscache package of Zimbra Collaboration Suite (ZCS) allows the Unix zimbra account to access files with root privileges. The passwordless sudo policy permits arbitrary arguments to zmunbound, whose wrapper forwards them to Unbound without restricting the configuration path. An attacker can supply a configuration that retains root privileges and disables the chroot. Include directives expose root-readable file contents through parser errors, while an attacker-selected logfile path creates a root-owned file or appends Unbound log records to an existing file. This can disclose password hashes and private keys and corrupt privileged configuration files, preventing affected services from starting with the modified configuration. The affected configuration is present in ZCS 10.1.16 and 10.1.21 dnscache packages.

Attack Chain
1
Initial Access

Attacker has low-privilege local access (e.g., via phishing or compromised service account)

2
Privilege Escalation

Attacker exploits CVE-2026-93640 to escalate from low-privilege user to root/SYSTEM/admin

3
Defense Evasion

Elevated privileges used to disable security controls, clear logs, and establish persistence

4
Impact

Full system compromise achieved; attacker can install ransomware, exfiltrate all data, or pivot

MITRE ATT&CK Techniques
T1068 Exploitation for Privilege Escalation
Privilege Escalation

Local attacker exploits vulnerability to gain root/SYSTEM privileges

T1134 Access Token Manipulation
Privilege Escalation

Elevated token used to impersonate high-privilege accounts

Indicators of Compromise
Type Value Description
user_agent Mozilla/5.0 (compatible; exploit/1.0) Generic exploit scanner user agent pattern
url /api/vuln-endpoint?payload=<malicious> Exploit attempt against application endpoint — monitor access logs for anomalous params
Remediation
1. Apply vendor-supplied security patches immediately. 2. If patches are unavailable, apply recommended mitigations from the vendor advisory. 3. Enable WAF rules or IDS signatures to detect exploitation attempts. 4. Monitor logs for indicators of compromise listed above. 5. Implement network segmentation to limit blast radius if exploitation occurs. 6. Subscribe to vendor security advisories for this product.
Quick Facts
CVE ID CVE-2026-93640
CVSS Score 7.8
Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published 2026-10-23
Exploited No
CISA KEV No
PoC Available
References
External Resources
NVD Entry BleepingComputer The Hacker News