CVE-2021-40506
📋 TL;DR
This vulnerability affects the OR1200 processor's ALU unit, where the overflow flag is not updated correctly for msb and mac instructions. This can cause software relying on this flag to experience execution corruption. Systems using the OR1200 processor from 2011-09-10 through 2015-11-11 are affected.
💻 Affected Systems
- OR1200 (OpenRISC 1200) processor
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through privilege escalation or remote code execution if exploited in critical software components.
Likely Case
Software crashes, data corruption, or incorrect calculations in applications that depend on overflow flag accuracy.
If Mitigated
Limited impact if affected systems are isolated and don't run software that relies on overflow flags.
🎯 Exploit Status
Exploitation requires specific conditions where software relies on the overflow flag for security decisions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit 2c0765d7ba12813df273cd693a99c4e744f0fbd5
Vendor Advisory: https://github.com/openrisc/or1200/commit/2c0765d7ba12813df273cd693a99c4e744f0fbd5
Restart Required: Yes
Instructions:
1. Update OR1200 processor firmware/hardware design
2. Recompile any affected software with updated processor specifications
3. Deploy updated hardware or firmware to affected systems
🔧 Temporary Workarounds
Avoid overflow-dependent software
allIdentify and avoid running software that relies on overflow flag accuracy
Software workaround implementation
allModify software to avoid using msb and mac instructions or implement software-based overflow checking
🧯 If You Can't Patch
- Isolate affected systems from critical networks and sensitive data
- Implement strict access controls and monitoring on affected systems
🔍 How to Verify
Check if Vulnerable:
Check processor version/revision and compare against affected date range (2011-09-10 to 2015-11-11)Check Version:
System-specific hardware/firmware version check commands vary by implementationVerify Fix Applied:
Verify processor firmware/hardware has been updated past the vulnerable date range📡 Detection & Monitoring
Log Indicators:
- Unexpected application crashes
- Calculation errors in software logs
- Processor exception logs
Network Indicators:
- Unusual traffic from affected systems if exploited
SIEM Query:
Search for application errors or crashes on systems with OR1200 processors