2026年6月24日の
セキュリティ情報

Subject: [Security Alert] Risks of Password Reuse and Unauthorized Access

Hi everyone,
We are sharing a reminder about the risks of "credential stuffing" attacks, where attackers use leaked usernames and passwords from one site to gain access to others.

What we need you to do:
1. Avoid using the same password across multiple services.
2. Enable multi-factor authentication (MFA) wherever possible.

Deadline: As soon as possible

Subject: [Security Alert] Beware of Phishing and Social Engineering Attacks

Dear employees,

Our security team has observed an increase in phishing and social engineering attacks designed to steal login credentials.

Requested Actions:
1. Do not click on links or open attachments from unknown or suspicious senders.
2. Immediately report any suspicious prompts asking for your password to the IT department.
3. Ensure that Multi-Factor Authentication (MFA) is enabled on all your accounts where available.

Deadline: Immediate (Please remain vigilant)

Subject: [Security Alert] Addressing GitHub CI/CD Workflow Vulnerability (Cordyceps)

Dear IT/Security Team,

We are sharing information regarding a critical vulnerability in GitHub CI/CD configurations codenamed 'Cordyceps'.

■ Overview
Due to weak CI/CD configurations, unauthenticated users can hijack workflows via pull requests (PRs), leading to arbitrary code execution and credential theft.

■ Scope
- Repositories utilizing CI/CD workflows (e.g., GitHub Actions).
- Specifically, those granting excessive permissions to PRs from external contributors.

■ Mitigation Steps
1. Review GitHub workflow configurations and audit permissions associated with `pull_request` events.
2. Ensure that PRs from external forks cannot access sensitive secrets or perform privileged operations without manual approval.
3. Explicitly define the `permissions` attribute in workflow files following the principle of least privilege.

■ Reference
- Novee Security Cordyceps Research

Priority: High
Deadline: Immediate review recommended

Subject: [Security Alert] Please Change Your Email Password (For KDDI Email Users)

Dear employees,

KDDI, a Japanese telecommunications provider, has announced a security incident where unauthorized access to their email service may have exposed user credentials.

Requested Actions:
1. If you use KDDI email services, please change your password immediately.
2. If you reuse the same password for other accounts, please change those as well.

Deadline: End of today

Subject: [Security Advisory] Tenable Identity Exposure Vulnerability Update

Dear IT/Security Team,

This is a notification regarding critical vulnerabilities identified in Tenable Identity Exposure.

■ Overview
Critical vulnerabilities have been discovered in versions of Tenable Identity Exposure prior to 3.93.4. A security update has been released to address these issues.

■ Scope
- Product: Tenable Identity Exposure
- Affected Versions: Prior to 3.93.4

■ Remediation Steps
1. Verify the current installed version of Tenable Identity Exposure.
2. Update the software to version 3.93.5 or later.

■ Reference
- Tenable Product Security Advisories

Priority: High
Deadline: Immediate