CVE-2018-25220 Overview
CVE-2018-25220 is a stack-based buffer overflow vulnerability in Bochs 2.6.5, an open-source IA-32 (x86) PC emulator. The flaw [CWE-787] allows attackers to execute arbitrary code by supplying an oversized input string to the application. Attackers construct a payload of 1200 bytes of padding followed by a return-oriented programming (ROP) chain that overwrites the saved instruction pointer and redirects execution to shell commands running with the privileges of the Bochs process.
Critical Impact
Successful exploitation grants attackers arbitrary code execution on the host running Bochs, with full confidentiality, integrity, and availability impact.
Affected Products
- Bochs 2.6.5 (cpe:2.3:a:bochs_project:bochs:2.6.5)
- Bochs Project distributions packaging the 2.6.5 release
- Downstream software that bundles the vulnerable Bochs 2.6.5 binary
Discovery Timeline
- 2026-03-28 - CVE-2018-25220 published to the National Vulnerability Database
- 2026-04-02 - Last updated in NVD database
Technical Details for CVE-2018-25220
Vulnerability Analysis
The vulnerability is an out-of-bounds write [CWE-787] on the stack. Bochs 2.6.5 copies attacker-controlled input into a fixed-size stack buffer without enforcing length validation. When the input exceeds the buffer capacity, adjacent stack frame data is overwritten, including the saved return address.
Because the corruption occurs on the call stack, attackers gain direct control of the instruction pointer when the vulnerable function returns. The Exploit-DB entry #43979 documents a working payload using 1200 bytes of padding to reach the saved EIP, followed by a return-oriented programming chain that pivots execution into chosen gadgets.
Exploitation results in arbitrary code execution within the Bochs process context. On systems where Bochs is invoked with elevated privileges or used as a sandboxing component, the impact extends to the underlying host operating system.
Root Cause
The root cause is missing bounds checking on a string copy operation into a fixed-size stack buffer. The application trusts the length of attacker-supplied input and performs the copy without comparing it against the destination buffer size, violating safe string handling practices.
Attack Vector
The attack vector is network-reachable in scenarios where Bochs processes input from remote sources, configuration files, or guest-supplied data. The attacker delivers a malicious string that triggers the overflow during parsing.
The documented exploit pattern places 1200 bytes of filler ahead of a ROP chain. Because modern binaries enable non-executable stacks, the ROP chain chains existing executable gadgets in Bochs and linked libraries to call functions such as system() with attacker-supplied arguments, producing shell command execution.
No verified proof-of-concept code is reproduced here. Refer to the Exploit-DB #43979 entry and the VulnCheck Advisory: Bochs 5 RCE for technical details.
Detection Methods for CVE-2018-25220
Indicators of Compromise
- Unexpected crashes or SIGSEGV events in the bochs process accompanied by corrupted stack traces.
- Child processes spawned from bochs that execute shell binaries such as /bin/sh, /bin/bash, or cmd.exe.
- Input files or network streams delivered to Bochs containing long contiguous byte sequences exceeding 1024 bytes followed by addresses pointing into loaded module ranges.
Detection Strategies
- Monitor process trees for bochs spawning interactive shells or networking utilities such as nc, curl, or wget.
- Alert on Bochs process crashes followed within seconds by new outbound connections from the same host.
- Inspect Bochs configuration files and guest images for oversized string fields that could trigger the overflow.
Monitoring Recommendations
- Enable core dump collection on systems running Bochs to capture stack corruption evidence for forensic review.
- Forward Bochs execution telemetry, including command-line arguments and child process events, to a centralized logging or SIEM platform.
- Audit hosts in the environment for installations of Bochs 2.6.5 using software inventory tooling.
How to Mitigate CVE-2018-25220
Immediate Actions Required
- Identify all systems running Bochs 2.6.5 and remove the binary where it is not required.
- Restrict execution of bochs to trusted users and prevent it from running with elevated privileges.
- Block untrusted input paths to Bochs, including untrusted configuration files and remote-supplied guest images.
Patch Information
The Bochs Project has released versions later than 2.6.5 that address memory safety issues. Upgrade to the latest available release from the Bochs Project Homepage. Validate that the deployed binary version is greater than 2.6.5 after upgrading.
Workarounds
- Run Bochs inside a restricted sandbox or container with no host filesystem or network access.
- Apply mandatory access control profiles such as AppArmor or SELinux to confine the bochs process.
- Disable Bochs on production systems until the upgrade is verified.
# Verify the installed Bochs version and remove vulnerable builds
bochs --version
# If output reports 2.6.5, remove the package or upgrade
# Debian/Ubuntu example
sudo apt-get remove --purge bochs
# Then install a current release from source after verifying the version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
