CVE-2025-12875
📋 TL;DR
This CVE describes an out-of-bounds write vulnerability in mruby 3.4.0's array handling function. Attackers with local access can manipulate arguments to cause memory corruption, potentially leading to arbitrary code execution. Systems using vulnerable mruby versions are affected.
💻 Affected Systems
- mruby
📦 What is this software?
Mruby by Mruby
⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation leading to full system compromise, arbitrary code execution as root/administrator, or complete data loss.
Likely Case
Local denial of service, application crashes, or limited privilege escalation within the mruby process context.
If Mitigated
Minimal impact with proper sandboxing and privilege separation, potentially limited to application crashes.
🎯 Exploit Status
Exploit requires local access and specific conditions to trigger the vulnerability. Public exploit code exists but requires understanding of mruby internals.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patched in commit 93619f06dd378db6766666b30c08978311c7ec94
Vendor Advisory: https://github.com/mruby/mruby/issues/6650
Restart Required: Yes
Instructions:
1. Update mruby to version containing commit 93619f06dd378db6766666b30c08978311c7ec94
2. Rebuild any applications using mruby
3. Restart affected services
🔧 Temporary Workarounds
Disable or sandbox mruby execution
allRestrict mruby execution to isolated environments with minimal privileges
Use containerization (Docker) with limited capabilities
Implement SELinux/AppArmor policies for mruby processes
Input validation wrapper
allAdd validation layer to check array bounds before passing to vulnerable functions
Implement custom wrapper functions that validate start/length parameters before calling ary_fill_exec
🧯 If You Can't Patch
- Implement strict access controls to limit local user access to systems running mruby
- Deploy runtime protection solutions that can detect and prevent out-of-bounds memory writes
🔍 How to Verify
Check if Vulnerable:
Check mruby version and verify if commit 93619f06dd378db6766666b30c08978311c7ec94 is present in the source codeCheck Version:
mruby --version or check mruby source repository for commit historyVerify Fix Applied:
Verify the patch commit exists in your mruby installation and test with known exploit PoC📡 Detection & Monitoring
Log Indicators:
- Segmentation fault logs from mruby processes
- Unexpected process termination of mruby applications
- Memory access violation errors
Network Indicators:
- None - local-only vulnerability
SIEM Query:
Process: mruby AND (EventID: 1000 OR Signal: SIGSEGV OR ExceptionCode: 0xc0000005)🔗 References
- https://github.com/makesoftwaresafe/mruby/commit/93619f06dd378db6766666b30c08978311c7ec94
- https://github.com/mruby/mruby/
- https://github.com/mruby/mruby/issues/6650
- https://github.com/mruby/mruby/issues/6650#event-20443453808
- https://github.com/mruby/mruby/issues/6650#issuecomment-3430851605
- https://vuldb.com/?ctiid.331511
- https://vuldb.com/?id.331511
- https://vuldb.com/?submit.680879
- https://github.com/mruby/mruby/issues/6650
- https://github.com/mruby/mruby/issues/6650#issuecomment-3430851605
