CVE-2021-3580 in nettle
Summary
by MITRE • 08/06/2021
A flaw was found in the way nettle's RSA decryption functions handled specially crafted ciphertext. An attacker could use this flaw to provide a manipulated ciphertext leading to application crash and denial of service.
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Analysis
by VulDB Data Team • 08/10/2021
The vulnerability identified as CVE-2021-3580 resides within the nettle cryptographic library's RSA decryption implementation, representing a significant security weakness that impacts numerous applications relying on this widely-used open-source library. This flaw specifically affects the handling of specially crafted ciphertext inputs during the RSA decryption process, where the library fails to properly validate or process malformed data, creating a predictable failure condition that can be exploited by malicious actors.
The technical nature of this vulnerability stems from insufficient input validation within the RSA decryption functions of the nettle library, which operates under the broader context of cryptographic protocol implementations. When an attacker provides manipulated ciphertext that triggers specific edge cases in the decryption algorithm, the library's processing routines encounter unexpected conditions that result in abrupt termination or system instability. This behavior aligns with CWE-248, which categorizes improper exception handling in software systems, and represents a classic example of an unchecked input condition that leads to program termination rather than graceful error recovery.
The operational impact of CVE-2021-3580 extends beyond simple application crashes to encompass broader denial of service conditions that can affect entire systems relying on nettle for cryptographic operations. Applications that depend on nettle for secure communications, digital signatures, or encrypted data processing become vulnerable to attacks that can render them unavailable to legitimate users. This vulnerability affects systems across multiple platforms including Linux distributions, embedded systems, and network infrastructure devices that utilize the nettle library for their cryptographic needs. The attack vector requires minimal sophistication, as an attacker only needs to craft specific ciphertext data that triggers the flawed processing path, making this vulnerability particularly dangerous in production environments where availability is critical.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected systems, as the nettle library has released updated versions that address the specific validation issues in the RSA decryption functions. System administrators should conduct comprehensive inventory assessments to identify all systems utilizing nettle, particularly those handling sensitive cryptographic operations, and deploy patches according to established security protocols. Organizations should also implement monitoring solutions to detect potential exploitation attempts, as the crash behavior can serve as an indicator of active attacks. The vulnerability's classification under ATT&CK technique T1499.004 for network denial of service provides additional context for threat detection and response planning, while adherence to secure coding practices such as input validation and proper error handling can prevent similar issues in future implementations. Organizations should also consider implementing additional security controls including network segmentation, intrusion detection systems, and regular security assessments to reduce the attack surface and improve overall resilience against exploitation attempts targeting cryptographic libraries.