2026年9月30日の
セキュリティ情報

Subject: [Urgent] Action Required: Citrix NetScaler CVE-2026-88772/88771

Dear IT/Security Team,

We are sharing critical information regarding the exploitation of vulnerabilities in Citrix NetScaler ADC and NetScaler Gateway.

■ Overview
Threat actors are exploiting CVE-2026-88772 and CVE-2026-88771 to bypass authentication and gain root-level access. Once access is established, attackers are deploying post-exploitation toolkits such as WHIPSHOT and SLAPSHOT.

■ Affected Products
- Citrix NetScaler ADC
- Citrix NetScaler Gateway

■ Required Actions
1. Immediately apply the latest security patches provided by Citrix to update your appliances to the latest version.
2. Review system logs for unexpected terminations of the NetScaler Packet Processing Engine (NSPPE) or the presence of unauthorized PHP web shells.

■ Reference
- Citrix Official Security Advisory

Priority: High
Deadline: Immediate

Subject: [Security Advisory] Zimbra Collaboration Suite CVE-2026-73570

Dear IT/Security Team,

We are sharing information regarding a critical vulnerability in Zimbra Collaboration Suite (ZCS).

■ Overview
An unauthenticated remote code execution (RCE) vulnerability (CVE-2026-73570, CVSS 8.9) is being exploited in the wild. Attackers use specially crafted SMTP requests to deploy JSP web shells, escalate privileges, and harvest authentication secrets from mailboxes.

■ Scope
- Product: Zimbra Collaboration Suite (ZCS)
- Condition: Systems with SNMP notifications enabled and the optional zimbra-snmp package installed.

■ Mitigation Steps
1. Update ZCS to version 10.1.20 or later immediately.
2. Consider removing the zimbra-snmp package if it is not required for business operations.
3. Audit logs for suspicious SMTP traffic and the presence of unauthorized JSP web shells.

■ Reference
- Zimbra Official Security Advisory

Priority: High
Deadline: Immediate

Subject: [Security Advisory] OpenSSL DTLS Vulnerability (CVE-2026-84782)

Dear team,

We are sharing information regarding a high-severity vulnerability in OpenSSL's DTLS implementation.

■ Overview
CVE-2026-84782 is a flaw where unencrypted heap memory can be leaked or the program can crash when a DTLS handshake message resend is triggered while a larger message is still being sent.

■ Affected Scope
- OpenSSL versions prior to 4.0.3, 3.6.5, 3.5.9, and 3.4.8.
- Specifically affects applications utilizing DTLS (TLS over UDP).

■ Mitigation Steps
1. Identify the OpenSSL versions used across your infrastructure and applications.
2. Update to the patched versions: 4.0.3, 3.6.5, 3.5.9, or 3.4.8.

■ Reference
- OpenSSL Official Advisory

Priority: High
Deadline: Immediate

Subject: [Security Alert] Leakage of Confidential Information via AI Tools

Dear employees,
It has been reported that AI coding agents may automatically upload internal company screenshots to public GitHub repositories, making sensitive data accessible to the public.

Requested Actions:
1. If you use AI agents to create or share screenshots, please verify that they are not being saved to public repositories.
2. Do not store any business-related data or screen captures in public locations, including personal GitHub accounts.

Deadline: Immediate

Subject: [Security Alert] Caution Regarding Suspicious Emails and Software Update Requests

Dear employees,

We have observed phishing campaigns that trick users into installing remote management software by disguising emails as meeting invitations or software update prompts.

Requested Actions:
1. Do not open attachments or click links in emails regarding "meeting invitations," "PDFs," or "software updates" from unknown or suspicious senders.
2. If you have accidentally executed a suspicious file or notice unfamiliar software installed on your device, please contact the IT department immediately.

Deadline: Immediate