CVE-2020-7226: Vt Cryptacular DOS Vulnerability

CVE-2020-7226 Overview

CVE-2020-7226 is a resource exhaustion vulnerability in CiphertextHeader.java within Cryptacular 1.2.3, a Java cryptographic library used by Apereo CAS and other products. The vulnerability allows remote attackers to trigger excessive memory allocation during a decode operation by supplying maliciously crafted input data. The flaw exists because the nonce array length associated with new byte[] allocation may depend on untrusted input within the header of encoded data, enabling attackers to cause denial of service conditions.

Critical Impact

Unauthenticated remote attackers can exhaust server memory resources by sending crafted encoded data, causing denial of service in applications using the vulnerable Cryptacular library including Apereo CAS, Oracle WebLogic Server, and Oracle WebCenter Sites.

Affected Products

• Cryptacular versions prior to patched releases
• Oracle Communications Services Gatekeeper 7.0
• Oracle WebCenter Sites 12.2.1.3.0 and 12.2.1.4.0
• Oracle WebLogic Server 12.2.1.4.0 and 14.1.1.0.0
• Apereo CAS (Central Authentication Service)

Discovery Timeline

• 2020-01-24 - CVE-2020-7226 published to NVD
• 2021-10 - Oracle releases security patches in October 2021 Critical Patch Update
• 2022-04 - Oracle releases additional security patches in April 2022 Critical Patch Update
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-7226

Vulnerability Analysis

The vulnerability resides in the CiphertextHeader.java class within the Cryptacular cryptographic library. During the decode operation, the library reads header information from encoded ciphertext data to reconstruct cryptographic parameters. A critical flaw exists in how the library handles the nonce length value extracted from this header.

When processing encoded data, the CiphertextHeader class extracts a length field from the input and uses it directly to allocate a byte array for storing the nonce. An attacker can craft malicious encoded data with an extremely large nonce length value in the header. Since this value is not properly validated before being used in a new byte[] allocation, the application attempts to allocate an arbitrarily large amount of memory based on attacker-controlled input.

This uncontrolled resource consumption can rapidly exhaust available heap memory, causing OutOfMemoryError exceptions and rendering the application unresponsive. In multi-user environments like Apereo CAS authentication servers or Oracle WebLogic applications, a single malicious request can impact service availability for all users.

Root Cause

The root cause is improper input validation (CWE-770: Allocation of Resources Without Limits or Throttling) in the header parsing logic. The CiphertextHeader class fails to implement reasonable bounds checking on the nonce length value before using it to allocate memory. The vulnerability occurs at the point where the library instantiates a new byte array using the untrusted length value from the encoded data header without validating that the value falls within acceptable bounds.

Attack Vector

The attack can be executed remotely over the network without authentication. An attacker sends specially crafted encoded data to any endpoint that processes ciphertext using the vulnerable Cryptacular library. The malicious data contains a manipulated header with an extremely large nonce length value.

When the target application attempts to decode this data, the CiphertextHeader.decode() method reads the attacker-controlled length value and attempts to allocate a correspondingly large byte array. This results in immediate memory exhaustion or forces the JVM garbage collector into an aggressive state, severely degrading application performance.

The attack is particularly effective against Apereo CAS deployments where cryptographic operations are performed during authentication flows. An unauthenticated attacker can repeatedly send malicious requests to exhaust server resources and deny service to legitimate users.

Detection Methods for CVE-2020-7226

Indicators of Compromise

• Sudden spikes in JVM heap memory usage without corresponding increase in legitimate traffic
• Repeated OutOfMemoryError exceptions in application logs related to byte array allocations
• Abnormal garbage collection activity with extended pause times
• Application unresponsiveness or timeout errors reported by users

Detection Strategies

• Monitor JVM heap memory metrics for anomalous allocation patterns, particularly large single allocations
• Implement application-level logging to capture and alert on ciphertext decode operations with unusually large parameters
• Deploy network-level inspection to identify requests with abnormally large encoded payload headers
• Configure heap dump analysis to identify memory exhaustion patterns associated with CiphertextHeader class allocations

Monitoring Recommendations

• Set up alerts for memory utilization exceeding normal operational thresholds
• Monitor application response times and error rates for degradation indicative of resource exhaustion
• Implement rate limiting on endpoints that process encoded cryptographic data
• Review application logs for patterns of failed decode operations or memory-related exceptions

How to Mitigate CVE-2020-7226

Immediate Actions Required

• Upgrade Cryptacular library to a patched version that implements proper input validation
• Apply Oracle Critical Patch Updates from October 2021 and April 2022 for affected Oracle products
• Review and update Apereo CAS deployments using the security fixes referenced in the GitHub CAS Pull Request
• Implement JVM heap size limits and garbage collection tuning to mitigate impact of memory exhaustion attacks

Patch Information

Patches are available from multiple sources depending on the affected product:

• Cryptacular: The vulnerability is tracked in Cryptacular Issue #52 with fixes applied to the CiphertextHeader.java class
• Apereo CAS: Multiple commits address the vulnerability including commit 8810f2b, commit 93b1c3e, and commit a042808
• Oracle Products: Apply patches from the Oracle October 2021 Security Alert and Oracle April 2022 Security Alert

Workarounds

• Implement request size limits at the web server or load balancer level to reject abnormally large payloads
• Configure JVM memory limits with -Xmx to prevent unbounded heap growth and enable faster failure detection
• Deploy a web application firewall (WAF) to inspect and filter requests with suspicious encoded data headers
• Implement application-level input validation to check encoded data sizes before processing

# JVM configuration to limit heap and enable memory monitoring
export JAVA_OPTS="-Xmx2g -Xms1g -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/log/heapdumps"

# Example nginx configuration to limit request body size
# Add to server block:
# client_max_body_size 10m;