CVE-2021-27378
📋 TL;DR
This vulnerability in the rand_core Rust crate allows attackers to seed random number generators with insufficient data, potentially compromising cryptographic security. It affects any Rust application using rand_core versions before 0.6.2 for generating cryptographic keys, tokens, or other security-sensitive random values.
💻 Affected Systems
- Rust applications using rand_core crate
📦 What is this software?
Rand Core by Rand Core Project
⚠️ Risk & Real-World Impact
Worst Case
Cryptographic keys become predictable, allowing attackers to decrypt sensitive data, forge authentication tokens, or compromise entire security systems.
Likely Case
Reduced entropy in random number generation weakens cryptographic operations, potentially enabling brute-force attacks or statistical analysis to predict values.
If Mitigated
With proper input validation and updated libraries, the risk is eliminated as proper buffer checks ensure sufficient seeding data.
🎯 Exploit Status
Exploitation requires understanding of the application's random number usage and ability to influence seeding data.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: rand_core 0.6.2 or later
Vendor Advisory: https://rustsec.org/advisories/RUSTSEC-2021-0023.html
Restart Required: Yes
Instructions:
1. Update Cargo.toml to require rand_core >= 0.6.2
2. Run 'cargo update rand_core'
3. Rebuild and redeploy your Rust application
4. Restart any running services using the updated application
🔧 Temporary Workarounds
Manual buffer validation
allAdd custom buffer length checks before calling read_u32_into or read_u64_into functions
// Add buffer length validation in your code
// Ensure buffer has sufficient capacity before calling vulnerable functions
🧯 If You Can't Patch
- Isolate affected applications from sensitive systems and networks
- Implement additional cryptographic validation layers for generated random values
🔍 How to Verify
Check if Vulnerable:
Check Cargo.lock or run 'cargo tree | grep rand_core' to see if version < 0.6.2 is usedCheck Version:
cargo tree | grep rand_coreVerify Fix Applied:
Verify rand_core version is >= 0.6.2 in Cargo.lock and rebuild application successfully📡 Detection & Monitoring
Log Indicators:
- Unusual cryptographic failures
- Random number generation errors
- Entropy source warnings
Network Indicators:
- Patterns in encrypted traffic suggesting weak keys
- Statistical anomalies in generated tokens
SIEM Query:
Search for applications using rand_core < 0.6.2 in dependency manifests or build logs