CVE-2026-87987 in Mistral Vibe
Summary
by MITRE • 09/11/2026
An arbitrary code execution vulnerability in Mistral Vibe allows an attacker to bypass command permission checks using environment variable assignments preceding allowlisted commands. These assignments are excluded from inspection, enabling attacker-controlled environment variables to cause arbitrary code execution without user approval.
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Analysis
by VulDB Data Team • 09/11/2026
The identified flaw represents a critical security weakness within the Mistral Vibe application architecture, specifically categorized under CWE-78 Improper Neutralization of Special Elements used in an OS Command commonly known as OS Command Injection. This vulnerability arises from a fundamental design error in how the software parses and validates user-supplied input before executing system-level commands. The core issue lies in the logic that processes command strings containing environment variable assignments, such as VAR=value followed by a legitimate executable. In many shell environments, these assignments are treated as context modifiers for the subsequent command rather than distinct arguments requiring independent validation. Mistral Vibe fails to inspect or sanitize these preceding environment variables, creating an exploitable gap where attacker-controlled data can influence the execution environment without triggering standard permission checks or allowlist verifications.
From a technical perspective, this vulnerability allows for privilege escalation and arbitrary code execution by manipulating the runtime context of allowed commands. When a user initiates a command that is on the system's allowlist, the application verifies only the base executable name against its whitelist. However, if an attacker can inject environment variable assignments before the whitelisted binary, these variables are passed directly to the operating system shell or interpreter without scrutiny. This mechanism enables the injection of malicious parameters such as LD_PRELOAD in Linux environments or other dynamic linker tricks that force the loading of shared libraries containing exploit code. Consequently, even though the final executed command is technically permitted by policy, the altered environment causes it to behave differently than intended, effectively bypassing security controls and executing arbitrary payloads with the privileges of the application process.
The operational impact of this vulnerability is severe, as it undermines the integrity of access control mechanisms designed to restrict user actions within the Mistral Vibe ecosystem. An authenticated attacker can leverage this flaw to execute system commands that were explicitly forbidden by administrative policies. This capability extends beyond simple command execution; it facilitates data exfiltration, lateral movement across networked systems if the application has broader connectivity, and potential full compromise of the underlying host operating system depending on the privileges assigned to the Mistral Vibe service account. The absence of user approval for these environment modifications means that standard interactive safeguards are rendered ineffective, allowing silent exploitation in automated or background processes as well.
To mitigate this risk, immediate remediation efforts should focus on hardening the input validation logic within the command execution module. Developers must implement strict parsing rules that either reject any command string containing environment variable assignments entirely or enforce rigorous sanitization of all components preceding the whitelisted executable. It is advisable to decouple environment configuration from user-supplied command arguments, ensuring that system variables are set through secure, internal mechanisms rather than being passed via external inputs. Additionally, adopting a principle of least privilege for the application runtime can limit the damage potential if exploitation occurs by restricting access to sensitive files and network resources. Regular security audits focusing on OS interaction patterns and adherence to CWE-78 guidelines will help prevent similar architectural flaws in future updates.