CVE-2026-42824: M365 Copilot Command Injection Information Disclosure

Technical summary

CVE-2026-42824 is a command injection flaw (CWE-77) in M365 Copilot stemming from improper neutralization of special elements in user-supplied input. The vulnerability permits an unauthenticated remote attacker to inject arbitrary commands that are processed by the application, leading to information disclosure. The attack requires user interaction (UI:R in the CVSS vector) and operates within a single security context (S:U). The network-accessible nature (AV:N) and low attack complexity (AC:L) mean that exploitation is straightforward once a victim engages with attacker-controlled input.

Business impact

Organizations relying on M365 Copilot for productivity face a targeted information disclosure risk. An attacker could craft a message, prompt, or input that tricks a user into triggering command injection, potentially exposing confidential documents, emails, or other sensitive data that Copilot can access. While the impact is limited to confidentiality (CVSS score 6.5, MEDIUM severity), the reputational and compliance implications of data leakage—especially for regulated industries—warrant prompt mitigation. Teams should assume that social engineering or phishing scenarios could be used to deliver malicious inputs to Copilot users.

Affected systems

Microsoft Copilot instances, including M365 Copilot deployments, are affected. The scope includes all versions unless explicitly patched. Organizations should verify their exact Copilot deployment model (web-based, plugin, desktop, or integrated within Office 365 applications) and check Microsoft's official advisory for specific build or version numbers requiring remediation.

Exploitability

Exploitation is moderately accessible. The attack vector is network-based and requires no special privileges, but it does require user interaction—the victim must actively engage with attacker-supplied input. This makes broad, indiscriminate attacks less effective than targeted phishing or social engineering campaigns. Once triggered, the injection succeeds reliably given the low attack complexity. The absence of KEV inclusion indicates this vulnerability has not yet been actively exploited in the wild at scale, though that status may change.

Remediation

Apply patches released by Microsoft for M365 Copilot to address command injection sanitization. Until patching is complete, organizations should educate users on scrutinizing unexpected or suspicious prompts, especially those originating from external communication channels. Consider restricting Copilot access to only trusted input sources where feasible, and monitor Copilot audit logs for unusual command patterns. Verify the specific patch version and deployment method in Microsoft's security advisory.

Patch guidance

Consult Microsoft's official security advisory for the specific patch version and release date applicable to your M365 Copilot deployment. Patches should be tested in a non-production environment before broad rollout to ensure compatibility with dependent workflows. Given the low-to-moderate severity and the requirement for user interaction, phased deployment is acceptable, but prioritize users who handle sensitive data or receive external communications. Confirm patch application through Microsoft's update mechanisms or administrative dashboards.

Detection guidance

Monitor for command injection indicators: unusual special characters or escape sequences in Copilot prompts (e.g., pipes, backticks, semicolons, $() constructs). Examine Copilot activity logs and audit trails for commands that deviate from normal user patterns or access unexpected data sources. Network-level detection is limited, but user-reported oddities—such as Copilot returning unrelated data—may signal exploitation attempts. Implement alerting on failed authentication or authorization attempts following Copilot interactions.

Why prioritize this

This vulnerability merits attention within 60 days despite its MEDIUM severity. The network accessibility and low complexity lower the barrier to attack, and information disclosure can expose high-value assets. However, the requirement for user interaction and the lack of active exploitation reduce urgency relative to remote code execution or privilege escalation flaws. Prioritize environments where Copilot has access to classified, financial, or personally identifiable information.

Risk score, explained

The CVSS 3.1 score of 6.5 reflects a MEDIUM-severity vulnerability with network accessibility (AV:N), low attack complexity (AC:L), no privilege requirement (PR:N), and required user interaction (UI:R). The impact is limited to confidentiality (C:H, I:N, A:N), meaning data may be disclosed but not corrupted or deleted. The single-context scope (S:U) constrains lateral movement or privilege escalation potential. This profile—high-value but narrow impact—justifies elevated attention in asset-rich environments without rising to CRITICAL status.

Frequently asked questions