CVE-2026-87985 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 ANSI-C quoted arguments. These arguments are not properly inspected, enabling a crafted allowlisted command to execute arbitrary code on the user's system without approval.
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Analysis
by VulDB Data Team • 09/11/2026
The identified vulnerability represents a critical security flaw within the Mistral Vibe application, specifically targeting its mechanism for handling and executing external commands through an interface that relies on permission checks. This issue stems from improper input validation regarding ANSI-C quoted arguments, which are a shell feature allowing for complex string manipulation and escape sequences. When users or automated systems submit allowlisted commands to the software, the system is designed to verify these inputs against a predefined whitelist of permitted operations before execution. However, the underlying implementation fails to adequately inspect the structure and content of ANSI-C quoted strings during this verification phase. This oversight creates a significant gap in the security boundary, allowing an attacker to craft malicious payloads that appear compliant with the allowlist rules while simultaneously containing executable code that bypasses the intended restrictions.
From a technical perspective, the core of the flaw lies in how the application parses and interprets ANSI-C escape sequences within command arguments. ANSI-C quoting allows for the inclusion of special characters such as newlines, tabs, and other control codes using backslash escapes like \n or \t. In many security implementations, these escape sequences are processed by the shell environment rather than the application itself during initial validation. If Mistral Vibe performs its permission checks on the raw input string before it is passed to a shell interpreter that processes ANSI-C quotes, an attacker can embed malicious commands within escaped characters that remain invisible or unvalidated until after the check has been completed. For instance, an argument might be structured in a way that satisfies the allowlist criteria for benign text but resolves into a command execution sequence once interpreted by the underlying system shell. This technique effectively neutralizes the protective measures intended to restrict user actions to safe operations only.
The operational impact of this vulnerability is severe, as it directly leads to arbitrary code execution on the victim's system without requiring explicit approval or authentication beyond what is already granted for using the application. An attacker who can influence the input parameters sent to Mistral Vibe could exploit this flaw to run any command available in the user environment with the same privileges as the running process. This capability allows for a wide range of malicious activities, including data exfiltration, installation of persistent backdoors, lateral movement within a network if the compromised system has access to other resources, and complete compromise of the host operating system. The severity is further amplified by the fact that the exploit relies on bypassing an allowlist mechanism, which typically provides users with a false sense of security regarding command safety.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) categories such as CWE-78 Improper Neutralization of Special Elements used in an OS Command and CWE-20 Incorrect Input Validation. The failure to properly sanitize or validate input before it interacts with the operating system shell is a classic example of command injection, specifically exploiting the nuances of how different quoting styles are processed by various components in the execution pipeline. Furthermore, from a tactical perspective related to the MITRE ATT&CK framework, this exploit technique corresponds to Command and Scripting Interpreter abuse, particularly involving indirect command invocation or argument injection. Attackers often use such methods to evade detection because they may not trigger standard signature-based defenses that look for obvious malicious strings in plain text arguments.
To mitigate this risk, developers must implement strict input validation that accounts for all possible encoding and quoting mechanisms supported by the target shell environment. This includes ensuring that permission checks are performed after any interpretation of escape sequences or ANSI-C quotes has occurred, rather than on the raw user input. Alternatively, the application should avoid passing untrusted data to system shells altogether by using native programming language functions for file operations and process management where possible. If shell execution is necessary, arguments must be passed as distinct array elements rather than concatenated into a single string that undergoes shell parsing. Additionally, implementing least privilege principles ensures that even if an exploit succeeds, the potential damage is contained within restricted permissions. Regular security audits focusing on command injection vectors and automated testing with fuzzing tools targeting ANSI-C quote handling can help identify similar weaknesses in other parts of the software ecosystem.