CVE-2012-0390 in GnuTLS
Summary
by MITRE
The DTLS implementation in GnuTLS 3.0.10 and earlier executes certain error-handling code only if there is a specific relationship between a padding length and the ciphertext size, which makes it easier for remote attackers to recover partial plaintext via a timing side-channel attack, a related issue to CVE-2011-4108.
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Analysis
by VulDB Data Team • 11/28/2021
The vulnerability identified as CVE-2012-0390 resides within the Datagram Transport Layer Security implementation of GnuTLS version 3.0.10 and earlier. This flaw represents a significant security weakness in the cryptographic protocol handling that governs secure communications over datagram networks. The issue specifically manifests in the error-handling mechanisms of the DTLS protocol implementation, where the execution of certain code paths depends on mathematical relationships between padding lengths and ciphertext dimensions. This dependency creates a predictable pattern that adversaries can exploit through sophisticated timing analysis techniques.
The technical flaw stems from the implementation's failure to maintain constant-time execution for all code paths during DTLS error handling. When processing malformed or corrupted datagram packets, the GnuTLS library exhibits variable execution times based on the relationship between padding length and ciphertext size. This timing variation occurs because the error-handling code only executes under specific conditions where padding length and ciphertext size meet predetermined mathematical criteria. Attackers can leverage this behavior to perform timing side-channel analysis, measuring the time differences in cryptographic operations to infer information about the encrypted data.
The operational impact of this vulnerability extends beyond simple information disclosure, creating a pathway for sophisticated attackers to recover partial plaintext data from encrypted communications. This vulnerability operates under the broader category of timing side-channel attacks, which are classified under CWE-388 and align with techniques documented in the MITRE ATT&CK framework under T1005 (Data from Local System) and T1041 (Exfiltration Over C2 Channel). The attack vector requires remote access to the target system, making it particularly dangerous for network services that rely on DTLS for secure communication.
The vulnerability's relationship to CVE-2011-4108 demonstrates a pattern of implementation weaknesses in cryptographic libraries where timing variations in error handling create exploitable conditions. This connection highlights the importance of constant-time implementation practices in cryptographic software development. The attack methodology relies on statistical analysis of timing measurements to reconstruct partial plaintext information, making it particularly effective against protocols that use padding schemes where the padding length is embedded within the ciphertext structure. Organizations using GnuTLS versions prior to 3.0.11 should urgently implement mitigations to prevent potential exploitation of this timing side-channel vulnerability.