CVE-2021-38296
📋 TL;DR
This vulnerability in Apache Spark allows attackers to recover full encryption keys from RPC connections using a flawed mutual authentication protocol. After an initial interactive attack, attackers can decrypt previously captured encrypted traffic offline. This affects Apache Spark deployments using RPC encryption with versions 3.1.2 and earlier.
💻 Affected Systems
- Apache Spark
📦 What is this software?
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Financial Services Crime And Compliance Management Studio by Oracle
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Spark by Apache
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain full access to decrypt all RPC communications, potentially exposing sensitive data, credentials, and internal system information transmitted between Spark components.
Likely Case
Attackers with network access can intercept and decrypt RPC traffic, potentially gaining access to job data, configuration details, and authentication information.
If Mitigated
With proper network segmentation and access controls, the attack surface is limited, but vulnerable systems remain at risk of traffic decryption if attackers gain initial access.
🎯 Exploit Status
Requires initial interactive attack to capture traffic, followed by offline key recovery. Attack complexity is moderate due to the need for network access and traffic interception.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apache Spark 3.1.3 or later
Vendor Advisory: https://lists.apache.org/thread/70x8fw2gx3g9ty7yk0f2f1dlpqml2smd
Restart Required: Yes
Instructions:
1. Download Apache Spark 3.1.3 or later from official Apache repository. 2. Stop all Spark services. 3. Replace existing Spark installation with patched version. 4. Restart Spark services. 5. Verify configuration settings remain intact.
🔧 Temporary Workarounds
Disable RPC Encryption
allDisable the vulnerable RPC encryption mechanism while maintaining other security controls
Set spark.authenticate=false and spark.network.crypto.enabled=false in spark-defaults.conf
Use Alternative Encryption
allEnable SASL encryption instead of the vulnerable RPC encryption
Set spark.authenticate.enableSaslEncryption=true in spark-defaults.conf
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Spark clusters from untrusted networks
- Monitor network traffic for unusual RPC communication patterns and implement intrusion detection
🔍 How to Verify
Check if Vulnerable:
Check Spark version and configuration: if version ≤ 3.1.2 AND spark.authenticate=true AND spark.network.crypto.enabled=true, system is vulnerableCheck Version:
spark-submit --version | grep 'version'Verify Fix Applied:
Verify Spark version is ≥ 3.1.3 and confirm RPC encryption settings are properly configured📡 Detection & Monitoring
Log Indicators:
- Failed authentication attempts on RPC ports
- Unusual RPC connection patterns
Network Indicators:
- Unusual traffic patterns on Spark RPC ports (default 7077)
- Multiple failed handshake attempts
SIEM Query:
source="spark*" AND (event_type="authentication_failure" OR port=7077) | stats count by src_ip