CVE-2025-7071 in ocrypto
Summary
by MITRE • 08/29/2025
Padding oracle attack vulnerability in Oberon microsystem AG’s ocrypto library in all versions since 3.1.0 and prior to 3.9.2 allows an attacker to recover plaintexts via timing measurements of AES-CBC PKCS#7 decrypt operations.
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Analysis
by VulDB Data Team • 08/29/2025
The vulnerability identified as CVE-2025-7071 represents a critical padding oracle attack flaw within the ocrypto library developed by Oberon microsystem AG. This weakness affects all versions from 3.1.0 through 3.9.1, creating a significant security risk for systems that rely on this cryptographic library for AES-CBC PKCS#7 decryption operations. The vulnerability stems from insufficient validation of padding during decryption processes, which creates observable timing variations that can be exploited by malicious actors to reconstruct sensitive plaintext data.
The technical implementation of this vulnerability resides in the cryptographic library's handling of padding validation during AES-CBC decryption operations. When the ocrypto library processes encrypted data using the AES-CBC mode with PKCS#7 padding, it exhibits differential timing behavior based on whether the padding is valid or invalid. This timing variation occurs because the library performs different execution paths for valid versus invalid padding, creating measurable differences that an attacker can exploit through careful timing measurements. The vulnerability specifically affects the PKCS#7 padding validation mechanism, where the library's response time varies depending on the padding correctness, enabling attackers to perform statistical analysis and gradually recover the plaintext through systematic probing.
From an operational perspective, this vulnerability poses severe implications for systems utilizing the affected ocrypto library, particularly those handling sensitive data through AES-CBC encryption. Attackers can leverage this weakness to perform plaintext recovery attacks without requiring direct access to encryption keys, making the exploitation particularly dangerous for applications processing confidential information such as personal data, financial records, or proprietary business information. The timing-based approach allows for efficient exploitation even over network connections, potentially enabling remote attackers to compromise data confidentiality without detection. Organizations using affected versions of the library face significant risk of data exposure, potential regulatory violations, and reputational damage from successful attacks.
The security implications of CVE-2025-7071 align with the Common Weakness Enumeration CWE-204, which categorizes this as a timing attack vulnerability resulting from observable differences in system behavior. This weakness also maps to ATT&CK technique T1005, where adversaries may leverage timing variations to extract sensitive information from cryptographic operations. The vulnerability demonstrates the critical importance of constant-time cryptographic implementations and proper padding validation mechanisms. Organizations should immediately upgrade to version 3.9.2 or later of the ocrypto library to remediate this vulnerability, as the patch addresses the timing discrepancies in padding validation and implements consistent response times regardless of padding correctness. Additionally, system administrators should conduct comprehensive vulnerability assessments to identify all instances of the affected library and implement monitoring for potential exploitation attempts.
This vulnerability underscores the broader challenge of cryptographic implementation security, where seemingly minor timing variations in processing can lead to significant information disclosure risks. The attack vector specifically targets the decryption phase of AES-CBC operations, making it particularly dangerous for systems that perform frequent decryption operations on sensitive data. The remediation process requires careful testing to ensure that upgrading the library does not introduce compatibility issues with existing applications, while also implementing additional security controls such as network monitoring for timing-based attacks and regular cryptographic audits to prevent similar vulnerabilities from emerging in other components.