CVE-2018-25258: RGui 3.5.0 Buffer Overflow Vulnerability

CVE-2018-25258 Overview

CVE-2018-25258 is a local buffer overflow vulnerability affecting RGui 3.5.0, the graphical user interface component of the R Project statistical computing environment. This vulnerability exists within the GUI preferences dialog and enables attackers to bypass Data Execution Prevention (DEP) protections through structured exception handling (SEH) exploitation. An attacker can craft malicious input in the "Language for menus and messages" field to trigger a stack-based buffer overflow, execute a Return-Oriented Programming (ROP) chain for VirtualAlloc allocation, and ultimately achieve arbitrary code execution on the target system.

Critical Impact

Local attackers can achieve arbitrary code execution by exploiting the buffer overflow in RGui's preferences dialog, bypassing DEP protections through SEH exploitation and ROP chain techniques.

Affected Products

• RGui 3.5.0 (Windows)
• R Project for Windows version 3.5.0

Discovery Timeline

• 2026-04-12 - CVE CVE-2018-25258 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2018-25258

Vulnerability Analysis

This vulnerability resides in the GUI preferences dialog component of RGui 3.5.0. The "Language for menus and messages" input field fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer. When an attacker provides specially crafted input exceeding the buffer's allocated size, the overflow overwrites adjacent stack memory, including the structured exception handler (SEH) chain.

The exploitation technique leverages SEH overwriting combined with ROP gadgets to bypass DEP protections. By carefully constructing the overflow payload, an attacker can redirect execution flow when an exception is triggered, using a ROP chain to call VirtualAlloc with executable permissions. This allows the attacker to allocate memory with execute rights and transfer control to their shellcode, achieving arbitrary code execution in the context of the RGui process.

The local attack vector requires the attacker to have access to the system where RGui is installed, but no authentication or user interaction is required beyond accessing the preferences dialog. The vulnerability affects the confidentiality, integrity, and availability of the affected system with high impact in all three areas.

Root Cause

The root cause is improper input validation in the GUI preferences dialog, specifically in the handling of the "Language for menus and messages" field. The application uses an unsafe string copy operation that does not enforce boundary checks, allowing user input to overflow the destination buffer on the stack. This is a classic stack-based buffer overflow vulnerability stemming from the use of unsafe memory handling functions without proper length validation.

Attack Vector

The attack requires local access to a system running RGui 3.5.0. The attacker must navigate to the GUI preferences dialog and input a maliciously crafted string in the "Language for menus and messages" field. The payload is constructed to:

1. Overflow the stack buffer and overwrite the SEH chain
2. Include a ROP chain that calls VirtualAlloc to allocate executable memory
3. Copy shellcode to the newly allocated executable memory region
4. Transfer execution to the shellcode, bypassing DEP protections

The exploitation technique demonstrates a sophisticated approach to defeating modern memory protections by combining SEH exploitation with ROP-based DEP bypass. For detailed technical information on the exploitation mechanism, see the Exploit-DB #46107 entry and the VulnCheck Advisory on RGUI.

Detection Methods for CVE-2018-25258

Indicators of Compromise

• Abnormal crash reports or exceptions originating from RGui.exe processes
• Unexpected memory allocation patterns or VirtualAlloc calls with PAGE_EXECUTE_READWRITE permissions from RGui
• Evidence of SEH chain manipulation in memory dumps or crash artifacts
• Suspicious process spawning or network connections from RGui.exe following user interaction with preferences dialog

Detection Strategies

• Monitor for abnormal VirtualAlloc API calls from RGui processes, particularly those requesting executable memory permissions
• Implement endpoint detection rules to identify ROP chain signatures or known exploitation patterns associated with SEH-based attacks
• Deploy memory protection monitoring to detect stack buffer overflow attempts and SEH corruption
• Use application whitelisting and behavioral analysis to identify anomalous RGui process behavior

Monitoring Recommendations

• Enable crash dump collection for RGui processes to capture exploitation attempts for forensic analysis
• Implement process monitoring to detect unexpected child processes spawned by RGui.exe
• Configure Windows Event Forwarding to centralize security events from endpoints running vulnerable R versions
• Deploy SentinelOne agents with behavioral AI to detect and block exploitation attempts targeting memory corruption vulnerabilities

How to Mitigate CVE-2018-25258

Immediate Actions Required

• Upgrade R for Windows to a patched version that addresses the buffer overflow vulnerability
• Restrict local access to systems running RGui 3.5.0 to trusted users only
• Consider uninstalling or disabling RGui if the graphical interface is not required for operations
• Implement application control policies to prevent unauthorized modification of R installations

Patch Information

Organizations should upgrade from R 3.5.0 to a newer version that addresses this vulnerability. The vulnerable installer can be found at the R Project Windows Installer archive (for reference purposes only). Users should visit the R Project Official Site to download the latest secure version of R for Windows.

Workarounds

• Disable or restrict access to the RGui preferences dialog through group policy or application restrictions
• Use R through command-line interfaces (Rterm.exe or Rscript.exe) instead of the graphical RGui component
• Implement exploit mitigation technologies such as EMET or Windows Defender Exploit Guard with additional protections enabled
• Deploy SentinelOne endpoint protection with behavioral AI capabilities to detect and block exploitation attempts targeting this vulnerability

# Configuration example: Restrict RGui execution via AppLocker
# Create a deny rule for RGui.exe on systems where GUI is not required
New-AppLockerPolicy -RuleType Path -Path "C:\Program Files\R\R-3.5.0\bin\Rgui.exe" -Action Deny -User Everyone