Vim Vulnerability Let Attackers Execute Arbitrary Command Via Weaponized Files

A high-severity security flaw has been discovered in Vim, one of the most widely used text editors among developers.

This vulnerability allows attackers to execute arbitrary operating system commands simply by tricking a user into opening a specially crafted file.

Discovered by security researcher Hung Nguyen, the bug chain highlights the persistent risks associated with how applications process embedded file instructions.

Vim Command Execution Vulnerability

The vulnerability stems from a two-part bug chain involving Vim’s modeline configuration feature and a flaw in its internal sandboxing mechanism.

In Vim, the tabpanel option accepts specific format strings, similar to the statusline and tabline options. However, unlike those secure options, tabpanel was inadvertently built without the crucial P_MLE security flag.

This flag normally ensures that the modelineexpr setting is explicitly enabled before allowing a modeline to process potentially dangerous expressions.

Because this security flag is completely missing, the standard modeline security checks are bypassed. An attacker can inject arbitrary expression strings into a file without needing the victim to have modelineexpr turned on.

While Vim correctly recognizes that the option was set insecurely and evaluates the expression in a restricted sandbox, a secondary flaw allows the attacker to escape it. The autocmd_add() function lacks a check_secure() verification call.

This critical omission allows the malicious sandboxed code to register an autocommand that quietly waits to execute until after the restricted sandbox environment has safely closed.

The exploitation process is highly dangerous because it requires zero user interaction beyond simply opening a file. Once the victim opens the weaponized document in a vulnerable version of Vim, the hidden payload executes automatically.

Granting the attacker arbitrary command execution with the same system privileges as the current user.

The attack surface for this vulnerability is notably broad. The modeline feature is enabled by default in Vim, and the exploit does not require the secondary modelineexpr setting to be active.

Furthermore, standard Vim builds include the tabpanel feature by default, meaning most out-of-the-box installations are susceptible to this command-injection attack.

Users and system administrators are strongly advised to update their software immediately.

The Vim development team has fixed the missing security checks and released a comprehensive patch on GitHub. Upgrading to Vim version 9.2.0272 or later will fully remediate the vulnerability and close the sandbox escape vector.

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