CVE-2018-25258 Overview
CVE-2018-25258 is a local stack-based buffer overflow vulnerability in RGui 3.5.0, the graphical user interface bundled with the R Project for Statistical Computing on Windows. The flaw exists in the GUI preferences dialog, specifically in the Language for menus and messages field. Attackers can supply oversized input to overwrite the Structured Exception Handler (SEH) chain, bypass Data Execution Prevention (DEP) using a Return-Oriented Programming (ROP) chain that calls VirtualAlloc, and achieve arbitrary code execution in the context of the local user.
Critical Impact
Successful exploitation grants attackers arbitrary code execution on Windows hosts running RGui 3.5.0, with full confidentiality, integrity, and availability impact on the affected system.
Affected Products
- R Project RGui 3.5.0 (Windows installer build)
- R for Windows base distribution 3.5.0
- Systems running the affected R Windows installer from R Project Windows Installer 3.5.0
Discovery Timeline
- 2026-04-12 - CVE-2018-25258 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2018-25258
Vulnerability Analysis
The vulnerability resides in the input handling routine of RGui's preferences dialog. RGui fails to validate the length of the string provided in the Language for menus and messages configuration field before copying it onto a fixed-size stack buffer. The oversized input overflows the buffer and overwrites the SEH record stored on the stack. When an exception is triggered later in execution, control transfers to an attacker-controlled handler pointer.
Because DEP is enforced on the process, attackers cannot execute shellcode directly from the stack. Instead, the exploit pivots into a ROP chain that calls VirtualAlloc to allocate a region of memory marked readable, writable, and executable. Shellcode is then copied into the new region and executed, completing the DEP bypass. Exploit-DB entry #46107 documents a working proof of concept for this technique.
Root Cause
The root cause is improper bounds checking on user-controlled configuration input in RGui 3.5.0, classified under [CWE-434]. The application copies attacker-controlled data into a stack buffer without enforcing length limits, allowing adjacent stack structures, including the SEH chain, to be corrupted.
Attack Vector
Exploitation requires local access to the host running RGui 3.5.0. An attacker, or a malicious R configuration file delivered via social engineering, supplies a crafted payload to the Language for menus and messages field. When RGui processes the input, the stack overflow is triggered, SEH is overwritten, and a ROP-based DEP bypass executes attacker shellcode. Full technical details are available in the VulnCheck Advisory on RGUI Buffer Overflow and the Exploit-DB #46107 entry.
No verified code examples are published in a redistributable form. Refer to the external Exploit-DB and VulnCheck references for the proof-of-concept payload structure, ROP gadget selection, and VirtualAlloc parameter staging.
Detection Methods for CVE-2018-25258
Indicators of Compromise
- Unexpected child processes spawned by Rgui.exe or Rterm.exe, particularly command shells or scripting hosts.
- Crash dumps referencing Rgui.exe with access violations in SEH dispatch routines.
- R configuration files (Rconsole, Rprofile) containing abnormally long values in language or locale fields.
Detection Strategies
- Monitor process creation events where Rgui.exe is the parent of cmd.exe, powershell.exe, rundll32.exe, or other living-off-the-land binaries.
- Hunt for memory allocations originating from Rgui.exe that request PAGE_EXECUTE_READWRITE permissions via VirtualAlloc.
- Inspect Windows Error Reporting and crash telemetry for repeated faults in Rgui.exe consistent with SEH corruption.
Monitoring Recommendations
- Enable command-line and module-load auditing on workstations where R 3.5.0 is installed.
- Track modifications to R user configuration files in %USERPROFILE% and shared profile locations.
- Alert on execution of legacy R 3.5.0 binaries in environments where upgraded versions are mandated.
How to Mitigate CVE-2018-25258
Immediate Actions Required
- Upgrade R for Windows to a current supported release from the R Project Official Website and remove R 3.5.0 binaries.
- Restrict execution of legacy Rgui.exe 3.5.0 using application control policies such as Windows Defender Application Control or AppLocker.
- Audit endpoints for the presence of the R 3.5.0 installer and remediate unmanaged installations.
Patch Information
No vendor-specific patch is published for RGui 3.5.0 because the affected release is end-of-life. Remediation requires upgrading to a current R for Windows version. The legacy installer remains available at R Project Windows Installer 3.5.0 for historical reference only and should not be deployed.
Workarounds
- Avoid opening untrusted R configuration files or project workspaces that may modify GUI preferences.
- Run R sessions under standard user accounts with no administrative rights to limit post-exploitation impact.
- Enforce DEP and Address Space Layout Randomization (ASLR) system-wide and enable Exploit Protection mitigations for Rgui.exe.
# Configuration example: enable Exploit Protection for Rgui.exe via PowerShell
Set-ProcessMitigation -Name Rgui.exe -Enable DEP,SEHOP,ForceRelocateImages,BottomUp,HighEntropy
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
