2026年10月5日の
セキュリティ情報

Subject: [Security Alert] Citrix NetScaler CVE-2026-88779 Mitigation

Dear IT/Security Team,

We are sharing information regarding a zero-day vulnerability affecting Citrix NetScaler.

■ Overview
CVE-2026-88779 is a memory overflow vulnerability in NetScaler ADC and NetScaler Gateway. Exploitation of this flaw can lead to a Denial of Service (DoS) condition. Targeted attacks have already been observed in the wild.

■ Scope
- Affected Products: NetScaler ADC, NetScaler Gateway
- Condition: Instances configured as SAML SP or SAML IdP

■ Action Plan
1. Apply the latest security patches provided by Citrix immediately.
2. Review SAML configurations and disable them if they are not required.
3. Monitor system logs for unexpected reboots or service unavailability.

■ Reference
- Citrix Official Security Advisory

Priority: High
Deadline: Immediate

Subject: [Security Advisory] Rejetto HFS CVE-2026-61500 Mitigation

Dear IT/Security Team,

We are sharing critical information regarding a vulnerability in Rejetto HFS.

■ Overview
A critical flaw (CVE-2026-61500, CVSS 9.3) has been identified in Rejetto HFS. The use of a weak PRNG (Math.random()) allows remote attackers to reconstruct the session signing key, forge administrator cookies, and achieve full administrative access, potentially leading to Remote Code Execution (RCE).

■ Affected Scope
- Product: Rejetto HTTP File Server (HFS)
- Versions: 3.0.0 through 3.2.0

■ Action Required
1. Identify if Rejetto HFS is deployed within the environment.
2. Immediately update the software to the latest patched version to mitigate the risk.

■ Reference
- VulnCheck Advisory

Priority: High
Deadline: Immediate

Subject: [Security Advisory] Microsoft Exchange Server CVE-2026-96940

Dear IT Administration Team,

We are sharing information regarding a high-severity vulnerability in Microsoft Exchange Server.

■ Overview
CVE-2026-96940 is a privilege escalation vulnerability (CVSS 8.8) that allows an authenticated attacker to gain unauthorized access to other users' mailboxes within the same organization, enabling them to read emails and attachments.

■ Scope
- Affected Products: Microsoft Exchange Server (On-premises)
*Note: Exchange Online customers are not affected as a service-side fix has been deployed.

■ Action Required
1. Verify the version of your on-premises Exchange Server installations.
2. Apply the latest security updates released by Microsoft immediately.

■ Reference
- Microsoft Official Security Advisory

Priority: High
Deadline: Immediate

Subject: [Security Alert] Please Update Your OS and Software

Hi everyone,
Recent security reports indicate that several vulnerabilities have been found in commonly used software, including iOS, Google Chrome, and WordPress.

What we need you to do:
1. Please apply any pending updates for your smartphone OS and web browser immediately.
2. Be cautious of suspicious emails and avoid clicking unknown links or attachments.

Deadline: By the end of this week

Subject: [Security Advisory] Progress Software (Sitefinity / Telerik Fiddler) Vulnerability Update

Dear IT/Security Team,

This is a notification regarding security vulnerabilities identified in Progress Software products.

■ Overview
Privilege escalation and security restriction bypass vulnerabilities have been discovered in Sitefinity Next.js Renderer and Telerik Fiddler Classic.

■ Affected Scope
- Progress Sitefinity Next.js Renderer: Versions prior to 15.4.8638
- Telerik Fiddler Classic for Windows: Version 6.0.20261.7291 and earlier

■ Mitigation Steps
1. Verify if the affected products and versions are deployed within the environment.
2. Update the software to the latest versions as specified by the vendor.

■ Reference
- Progress Software Official Security Bulletins

Priority: High
Deadline: Immediate