CVE-2019-1105 is a spoofing vulnerability identified in Microsoft Outlook for Android, specifically affecting version 1.0 of the application. The vulnerability arises from improper parsing of specially crafted email messages by the Outlook client on Android devices. An authenticated attacker—meaning one who can send emails to the victim's inbox—can exploit this flaw by sending a maliciously constructed email that tricks the Outlook app into misrepresenting the sender or message content. This spoofing can facilitate cross-site scripting (XSS) attacks within the context of the Outlook app, allowing the attacker to execute arbitrary scripts with the privileges of the current user. Such script execution could lead to unauthorized actions, data theft, or further compromise of the device or user data. The vulnerability is rooted in the email parsing logic, and Microsoft addressed it by releasing a security update that corrects how Outlook for Android processes these crafted messages. Notably, there are no known exploits in the wild reported for this vulnerability, and no CVSS score has been assigned. The attack requires the victim to receive and open the malicious email, but no additional user interaction beyond viewing the message is explicitly required. The vulnerability impacts confidentiality and integrity primarily, as it could allow attackers to impersonate trusted senders and execute scripts to manipulate or exfiltrate data. Availability impact is likely limited. Since the vulnerability is in a widely used mobile email client, the scope includes any Android user running the affected Outlook version who receives emails from potentially malicious senders.

For European organizations, this vulnerability poses a risk primarily through targeted phishing or spear-phishing campaigns leveraging the spoofing capability to impersonate trusted contacts or internal personnel. Successful exploitation could lead to unauthorized access to sensitive corporate communications, credential theft, or deployment of further malware via script execution. Given the widespread use of Microsoft Outlook for Android among enterprise users in Europe, especially in sectors with high email reliance such as finance, government, and professional services, the potential for data breaches or espionage is significant. The vulnerability could undermine trust in email communications and facilitate lateral movement within corporate networks if attackers leverage the XSS to escalate privileges or harvest credentials. However, the requirement for the attacker to send a crafted email and the absence of known active exploits somewhat limit immediate widespread impact. Still, organizations with mobile-first workforces or BYOD policies are particularly vulnerable, as mobile devices often have less stringent security controls than desktops. The confidentiality and integrity of communications are the main concerns, with potential regulatory implications under GDPR if personal or sensitive data is compromised.

European organizations should prioritize updating Microsoft Outlook for Android to the latest patched version to remediate this vulnerability. Beyond patching, organizations should implement advanced email filtering and anti-spoofing technologies such as DMARC, DKIM, and SPF to reduce the likelihood of malicious emails reaching end users. User awareness training should emphasize caution with unexpected or suspicious emails, even from known contacts, and encourage reporting of anomalies. Mobile device management (MDM) solutions can enforce application updates and restrict installation of outdated or vulnerable apps. Additionally, organizations should monitor email traffic for signs of spoofing or phishing attempts and employ endpoint detection and response (EDR) tools on mobile devices to detect abnormal script execution or behavior. Network segmentation and the principle of least privilege can limit the impact if a device is compromised. Finally, incident response plans should include procedures for mobile device compromise scenarios to ensure rapid containment and remediation.