CVE-2022-38493 in Rhonabwy
Summary
by MITRE • 08/21/2022
Rhonabwy 0.9.99 through 1.1.x before 1.1.7 doesn't check the RSA private key length before RSA-OAEP decryption. This allows attackers to cause a Denial of Service via a crafted JWE (JSON Web Encryption) token.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/24/2022
The vulnerability identified as CVE-2022-38493 affects the Rhonabwy library version 0.9.99 through 1.1.x before 1.1.7, specifically targeting the RSA-OAEP decryption implementation. This flaw represents a critical security weakness that enables malicious actors to exploit the cryptographic library through crafted JSON Web Encryption tokens. The issue stems from insufficient validation of RSA private key parameters during the decryption process, creating a pathway for adversaries to manipulate the cryptographic operations and potentially disrupt service availability.
The technical root cause of this vulnerability lies in the absence of proper RSA private key length verification before executing RSA-OAEP decryption operations. When processing JSON Web Encryption tokens, the library fails to validate whether the provided RSA private key meets the minimum security requirements or expected parameter constraints. This validation gap allows attackers to submit specially crafted JWE tokens containing manipulated RSA key parameters that can trigger unexpected behavior in the decryption routine. The vulnerability specifically impacts the RSA-OAEP decryption algorithm which requires specific key length parameters to function correctly, and when these parameters are outside expected ranges, the decryption process becomes vulnerable to exploitation.
The operational impact of this vulnerability manifests primarily as a Denial of Service condition that can be triggered by any user or system capable of submitting crafted JWE tokens to the affected library. Attackers can construct malicious tokens that, when processed by the vulnerable Rhonabwy library, cause the decryption routine to either crash, hang indefinitely, or consume excessive system resources. This creates a reliable vector for service disruption attacks that can affect any application or system relying on the affected library for JSON Web Encryption processing. The vulnerability is particularly concerning because it can be exploited without requiring authentication or privileged access, making it an attractive target for attackers seeking to disrupt services.
From a cybersecurity perspective, this vulnerability maps to CWE-327 (Use of a Broken or Risky Cryptographic Algorithm) and CWE-20 (Improper Input Validation) within the Common Weakness Enumeration framework. The flaw demonstrates poor cryptographic implementation practices that violate fundamental security principles for key parameter validation. Additionally, this vulnerability aligns with ATT&CK technique T1499.004 (Endpoint Denial of Service) and could be leveraged as part of broader attack chains targeting application availability. The weakness represents a failure in proper cryptographic library design where input validation should occur before cryptographic operations are executed, a principle that should be enforced in accordance with NIST SP 800-57 and other cryptographic standards.
The recommended mitigation strategy involves upgrading to Rhonabwy version 1.1.7 or later, which contains the necessary fixes to properly validate RSA private key lengths before RSA-OAEP decryption operations. Organizations should also implement additional monitoring for unusual decryption patterns or resource consumption that might indicate exploitation attempts. Network-level protections such as rate limiting and input validation at the application boundary can provide additional defense-in-depth measures. Security teams should conduct thorough inventory assessments to identify all systems utilizing the vulnerable library versions and prioritize remediation efforts based on the criticality of affected services. Regular security assessments and dependency updates should be implemented to prevent similar vulnerabilities from emerging in other cryptographic components.