2026年5月15日の
セキュリティ情報

Subject: [Security Alert] Caution Regarding Suspicious Emails (Microsoft Exchange Vulnerability)

Dear employees,

A vulnerability has been discovered in Microsoft Exchange Server that could allow malicious scripts to run if a specially crafted email is opened.

Requested Actions:
1. Do not open emails from unknown senders or emails containing suspicious links or attachments.
2. If you have opened a suspicious email and notice any unusual browser behavior, please report it to the IT department immediately.

Deadline: Immediate / Ongoing

件名: 【共有】Microsoft Exchange Server CVE-2026-42897 対応について

お疲れさまです。Exchange Serverのゼロデイ脆弱性に関する情報共有です。

■ 概要
Outlook on the webにおいて、XSSを利用してブラウザコンテキストで任意のJavaScriptを実行可能な脆弱性（CVE-2026-42897）が確認されました。現在、攻撃による悪用が報告されています。

■ 影響範囲
- Exchange Server 2016
- Exchange Server 2019
- Exchange Server Subscription Edition (SE)

■ 対応手順
1. Exchange Emergency Mitigation Service (EEMS) が有効であることを確認し、自動緩和策を適用させる。
2. EEMSを無効にしている場合は、速やかに有効化することを検討する。
3. Microsoftから恒久的なセキュリティ更新プログラムがリリースされ次第、適用計画を策定する。

■ 参考情報
- Microsoft 公式アドバイザリ

対応優先度: 高
対応期限: 速やかに

Subject: [Technical Alert] Mitigation for Microsoft Exchange Server CVE-2026-42897

Dear IT/Security Team,

This is a notification regarding a zero-day vulnerability in Microsoft Exchange Server.

■ Overview
CVE-2026-42897 is a high-severity spoofing/XSS vulnerability that allows arbitrary JavaScript execution in the browser context when a user opens a crafted email via Outlook on the web. Active exploitation has been reported.

■ Affected Scope
- Exchange Server 2016
- Exchange Server 2019
- Exchange Server Subscription Edition (SE)

■ Mitigation Steps
1. Ensure the Exchange Emergency Mitigation Service (EEMS) is enabled to receive automatic mitigations.
2. If EEMS is currently disabled, enable it immediately to mitigate the risk.
3. Monitor for the release of official security patches and apply them as soon as they become available.

■ Reference
- Microsoft Official Advisory

Priority: High
Deadline: Immediate

Subject: [Action Required] Please Update Your Browser and OS

Dear employees,
Recent reports from a global hacking competition have revealed critical vulnerabilities in widely used software, including Microsoft Edge and Windows 11.

Requested Actions:
1. Run Windows Update to ensure your operating system is up to date.
2. If your browser (e.g., Microsoft Edge) prompts for an update, please restart it to apply the changes immediately.

Deadline: End of today

件名: 【共有】Pwn2Own Berlin 2026におけるゼロデイ脆弱性報告について

お疲れさまです。Pwn2Own Berlin 2026初日の戦報に関する情報共有です。

■ 概要
Microsoft Edgeのサンドボックス脱出（論理脆弱性の連鎖）、Windows 11の権限昇格、NVIDIA Container Toolkit、Red Hat Linux、および複数のAIプラットフォーム（LiteLLM, OpenAI Codex, LM Studio）におけるゼロデイ脆弱性が実証されました。

■ 影響範囲
- Microsoft Edge
- Windows 11
- NVIDIA Container Toolkit
- Red Hat Linux Workstation
- LiteLLM, OpenAI Codex, LM Studio

■ 対応手順
1. 対象製品のベンダーから公開されるセキュリティアドバイザリを監視し、パッチを適用する。
2. AIプラットフォームやコンテナ環境において、不必要な外部アクセスを制限し、SSRF等のリスクを低減させる。

■ 参考情報
- Zero Day Initiative (ZDI) 公式発表

対応優先度: 高
対応期限: パッチ公開後速やかに

Subject: [Info] Zero-Day Vulnerabilities Reported at Pwn2Own Berlin 2026

Dear team,
This is a technical update regarding the first day of Pwn2Own Berlin 2026.

■ Overview
Several zero-day vulnerabilities were demonstrated, including a complex logic-based sandbox escape in Microsoft Edge, privilege escalation in Windows 11, and flaws in NVIDIA Container Toolkit and Red Hat Linux. AI platforms (LiteLLM, OpenAI Codex, LM Studio) were also heavily targeted via SSRF and code injection.

■ Scope
- Microsoft Edge
- Windows 11
- NVIDIA Container Toolkit
- Red Hat Linux Workstation
- LiteLLM, OpenAI Codex, LM Studio

■ Mitigation Steps
1. Monitor vendor security advisories and apply patches as soon as they are released.
2. Implement strict network egress filtering for AI platforms and container environments to mitigate SSRF risks.

■ Reference
- Zero Day Initiative (ZDI) official announcements

Priority: High
Deadline: Immediately upon patch release

Subject: [Security Alert] Critical Nginx Vulnerability (CVE-2026-42945)

Dear IT Administration Team,

We are sharing information regarding a critical vulnerability discovered in Nginx.

■ Overview
A heap buffer overflow vulnerability (CVE-2026-42945) has been identified in the ngx_http_rewrite_module. With a CVSS v4.0 score of 9.2, this flaw allows unauthenticated attackers to cause a server restart via specially crafted HTTP requests. In environments where ASLR is disabled, arbitrary code execution is possible.

■ Affected Scope
- Nginx Plus R32 to R36
- Nginx Open Source (versions prior to 1.30.0)
- Nginx Instance Manager
- Nginx Ingress Controller

■ Mitigation Steps
1. Identify all Nginx instances and their current versions.
2. Update to the latest patched version provided by F5.

■ Reference
- F5 Official Security Advisory

Priority: High
Deadline: Immediate

Subject: [Urgent] Cisco Catalyst SD-WAN CVE-2026-20182 Mitigation

Dear IT Security Team,

We are sharing critical information regarding a zero-day vulnerability in Cisco Catalyst SD-WAN products.

■ Overview
CVE-2026-20182 is a critical vulnerability affecting Catalyst SD-WAN Controller and Manager. Threat actor UAT-8616 is actively exploiting this to gain root access, add unauthorized SSH keys, and modify NETCONF configurations for persistence.

■ Affected Scope
- Catalyst SD-WAN Controller
- Catalyst SD-WAN Manager (formerly vManage)

■ Action Plan
1. Immediately apply the latest security patches provided by Cisco PSIRT.
2. Audit SSH authorized_keys for any unauthorized entries.
3. Review NETCONF configuration logs for suspicious modifications.

■ Reference
- Cisco Talos Intelligence Group official advisory

Priority: High
Deadline: Immediate

Subject: [Action Required] Please Update Your Browser and Windows OS

Dear employees,
Critical vulnerabilities have been discovered in Microsoft Edge and Windows 11 during a global security competition. These flaws could potentially allow attackers to gain unauthorized access to your system.

Requested Actions:
1. Run Windows Update to ensure your operating system is up to date.
2. Check for updates in Microsoft Edge by navigating to Help -> About Microsoft Edge.

Deadline: End of today

件名: 【共有】Pwn2Own Berlin 2026におけるEdge/Windows 11/LiteLLMの脆弱性について

お疲れさまです。Pwn2Own Berlin 2026にて報告された脆弱性に関する情報共有です。

■ 概要
Microsoft Edgeのサンドボックス脱出（4つの論理脆弱性の連鎖）、Windows 11の権限昇格（ヒープバッファオーバーフロー等）、およびLiteLLMのRCE（SSRFとコード注入の組み合わせ）が実証されました。AIプラットフォームや推論エンジンが新たな攻撃対象となっている傾向が見られます。

■ 影響範囲
- Microsoft Edge
- Windows 11
- LiteLLM
- OpenAI Codex / NVIDIA Megatron Bridge / NV Container Toolkit

■ 対応手順
1. 影響を受ける製品の最新パッチ適用状況を確認し、未適用の場合は速やかに更新を配信する。
2. AI開発環境において、外部入力のサニタイズおよびAPIアクセス制御が適切に設定されているかレビューする。

■ 参考情報
- Zero Day Initiative (ZDI) 公式発表

対応優先度: 高
対応期限: パッチ公開後速やかに

Subject: [Technical Info] Vulnerabilities in Edge, Windows 11, and LiteLLM (Pwn2Own Berlin 2026)

Dear Security Team,

This is a technical update regarding the zero-day exploits demonstrated at Pwn2Own Berlin 2026.

■ Overview
Researchers successfully demonstrated a sophisticated sandbox escape in Microsoft Edge via a chain of four logical flaws, and privilege escalation in Windows 11 using heap-based buffer overflows. Additionally, LiteLLM was compromised through a chain involving SSRF and code injection, indicating a shift in threat landscapes toward AI infrastructure.

■ Scope
- Microsoft Edge
- Windows 11
- LiteLLM
- OpenAI Codex, NVIDIA Megatron Bridge, NV Container Toolkit

■ Mitigation Steps
1. Monitor and deploy the latest security updates for Windows 11 and Microsoft Edge.
2. Audit AI framework deployments (e.g., LiteLLM) for proper input validation and API security.

■ Reference
- Zero Day Initiative (ZDI) official reports

Priority: High
Deadline: Immediate upon patch availability