CVE-2021-29940
📋 TL;DR
This vulnerability in the Rust 'through' crate allows double-free memory corruption when the map function panics. Attackers could exploit this to execute arbitrary code or crash applications. Any Rust application using the affected through crate versions is vulnerable.
💻 Affected Systems
- Rust through crate
📦 What is this software?
Through by Through Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Application crashes causing denial of service and potential memory corruption that could be leveraged for further exploitation.
If Mitigated
Limited impact if applications run with memory safety protections like ASLR and DEP, though crashes may still occur.
🎯 Exploit Status
Exploitation requires triggering a panic in the map function, which may be possible with crafted input. The advisory includes proof-of-concept details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to through crate version after 2021-02-18
Vendor Advisory: https://rustsec.org/advisories/RUSTSEC-2021-0049.html
Restart Required: Yes
Instructions:
1. Update Cargo.toml to use through crate version > 2021-02-18. 2. Run 'cargo update --package through'. 3. Rebuild and redeploy your application.
🔧 Temporary Workarounds
Avoid panic-prone map functions
allModify code to avoid using map functions that could panic with the through crate
Pin older version with patch
allIf you must use older versions, apply the fix from the advisory manually
cargo update --package through --precise <fixed-version>
🧯 If You Can't Patch
- Isolate affected applications in containers or VMs with minimal privileges
- Implement network segmentation to limit attack surface and monitor for crash events
🔍 How to Verify
Check if Vulnerable:
Check Cargo.lock for through crate version <= 0.3.6 or date <= 2021-02-18Check Version:
grep through Cargo.lock | grep versionVerify Fix Applied:
Verify through crate version > 0.3.6 in Cargo.lock after update📡 Detection & Monitoring
Log Indicators:
- Application crashes with double-free errors
- Panic messages from through crate map operations
Network Indicators:
- Unusual traffic patterns to applications using through crate
SIEM Query:
source="application.logs" AND ("double free" OR "through crate panic")