CVE-2019-25695: R 3.4.4 Buffer Overflow Vulnerability

CVE-2019-25695 Overview

CVE-2019-25695 is a local buffer overflow vulnerability in R 3.4.4 that allows attackers to execute arbitrary code through the GUI Preferences language field. This vulnerability is classified as CWE-787 (Out-of-Bounds Write), which occurs when the application writes data past the end of an allocated buffer.

The vulnerability can be exploited by crafting a malicious payload with a 292-byte offset and JMP ESP instruction, which is then pasted into the "Language for menus and messages" field within the GUI Preferences. When successfully exploited, an attacker can execute arbitrary commands on the target system.

Critical Impact

This local buffer overflow vulnerability enables arbitrary code execution on systems running R 3.4.4, potentially allowing attackers to gain complete control of affected workstations through GUI manipulation.

Affected Products

• R 3.4.4 for Windows

Discovery Timeline

• 2026-04-12 - CVE CVE-2019-25695 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2019-25695

Vulnerability Analysis

This vulnerability stems from improper bounds checking in the R GUI Preferences handler when processing user-supplied input in the language configuration field. The application fails to validate the length of data being written to a fixed-size buffer, creating a classic stack-based buffer overflow condition.

When a user pastes specially crafted input exceeding the expected buffer size into the "Language for menus and messages" field, the overflow corrupts adjacent stack memory including the return address. By precisely controlling the overflow with a 292-byte offset, an attacker can overwrite the return pointer with a JMP ESP instruction address, redirecting execution to attacker-controlled shellcode.

This is a local attack vector, meaning an attacker would need either physical access to the machine or the ability to trick a user into pasting the malicious payload. The lack of authentication requirements and user interaction beyond pasting the payload makes this vulnerability particularly dangerous in environments where R is used for data analysis.

Root Cause

The root cause is a failure to perform proper bounds checking on user input in the GUI Preferences language field handler. The application allocates a fixed-size buffer for the language setting but does not validate that user input fits within this allocation before copying data. This allows an attacker to overflow the buffer by supplying input larger than the allocated space.

Attack Vector

The attack requires local access to the system running R 3.4.4. An attacker crafts a payload containing:

1. Padding data (292 bytes) to reach the return address on the stack
2. The address of a JMP ESP instruction to redirect execution
3. Shellcode to execute arbitrary commands (such as launching calc.exe as a proof-of-concept)

The payload is delivered by pasting it into the "Language for menus and messages" field in the R GUI Preferences dialog. When the application processes this input, the buffer overflow occurs, and the embedded shellcode executes with the privileges of the current user.

A public exploit is documented in Exploit-DB #46265, and additional technical details can be found in the VulnCheck Advisory.

Detection Methods for CVE-2019-25695

Indicators of Compromise

• Unexpected child processes spawned by Rgui.exe or R.exe (e.g., calc.exe, cmd.exe, powershell.exe)
• Crash dumps or application errors from R indicating stack corruption
• Unusual clipboard activity involving large binary payloads pasted into R application windows

Detection Strategies

• Monitor R GUI processes for anomalous child process creation, particularly command shells or scripting interpreters
• Deploy endpoint detection rules to identify buffer overflow exploitation patterns such as NOP sleds followed by shellcode signatures
• Implement application whitelisting to prevent execution of unauthorized binaries spawned from R processes

Monitoring Recommendations

• Enable Windows Event Logging for process creation (Event ID 4688) and monitor for Rgui.exe spawning unexpected child processes
• Configure EDR solutions to alert on stack pivot or ROP chain detection in processes associated with R
• Review system logs for R application crashes that may indicate exploitation attempts

How to Mitigate CVE-2019-25695

Immediate Actions Required

• Upgrade R to a version later than 3.4.4 from the R Project Windows Binaries repository
• Restrict access to systems running vulnerable versions of R to trusted users only
• Consider deploying Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) enforcement to mitigate buffer overflow exploitation

Patch Information

Users should upgrade to a newer version of R that addresses this vulnerability. The latest R binaries for Windows can be obtained from the official R Project Windows Binaries repository. Verify the integrity of downloaded packages using provided checksums before installation.

Workarounds

• Avoid pasting untrusted content into R GUI preference fields
• Use the command-line version of R (Rscript or R.exe in terminal mode) instead of the GUI where possible to avoid the vulnerable code path
• Implement strict access controls on workstations running R 3.4.4 to limit potential attackers

For environments where immediate upgrade is not feasible, consider running R in a sandboxed or containerized environment to limit the impact of potential exploitation.