CVE-2015-7511 in Libgcrypt
Summary
by MITRE
Libgcrypt before 1.6.5 does not properly perform elliptic-point curve multiplication during decryption, which makes it easier for physically proximate attackers to extract ECDH keys by measuring electromagnetic emanations.
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Analysis
by VulDB Data Team • 11/18/2024
The vulnerability identified as CVE-2015-7511 affects Libgcrypt versions prior to 1.6.5 and represents a significant side-channel attack vector targeting elliptic curve cryptography implementations. This flaw specifically impacts the ECDH (Elliptic Curve Diffie-Hellman) key exchange mechanism where the cryptographic library fails to properly execute elliptic-point curve multiplication during decryption operations. The vulnerability stems from insufficient protection against electromagnetic side-channel analysis, creating an exploitable weakness that allows attackers to recover sensitive cryptographic keys through passive measurement of electromagnetic emanations.
The technical implementation flaw occurs within the cryptographic library's handling of elliptic curve operations, where the multiplication process lacks proper countermeasures against side-channel attacks. During decryption operations, the library's implementation of elliptic-point curve multiplication does not sufficiently obscure the computational patterns that reveal information about the secret keys. This weakness enables attackers to perform electromagnetic analysis and correlate measurement data with the underlying cryptographic operations. The vulnerability is particularly concerning because it requires only physical proximity to the target system, making it accessible to attackers who can position themselves near the device being attacked. The attack exploits the relationship between the electromagnetic emissions and the mathematical operations performed during elliptic curve calculations, allowing for key recovery through statistical analysis of the measured signals.
From an operational perspective, this vulnerability creates a substantial risk for systems relying on Libgcrypt for ECDH key exchange operations, particularly in environments where physical security controls may be insufficient. The attack vector is especially dangerous in scenarios where attackers can gain physical access to devices or are located in close proximity to target systems, such as in office environments, data centers, or other facilities where electromagnetic emissions can be captured. The impact extends beyond simple key recovery to potentially compromise entire cryptographic protocols that depend on ECDH for secure key exchange, affecting communications security, authentication systems, and any application relying on the affected Libgcrypt versions. Organizations using affected software may experience unauthorized access to encrypted communications, compromised digital signatures, and potential data breaches through the recovery of private keys used in elliptic curve cryptographic operations.
The vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in the implementation of cryptographic algorithms, and relates to the broader category of side-channel attacks that fall under ATT&CK technique T1552.005 for credentials from password storage. Mitigation strategies should include immediate upgrade to Libgcrypt version 1.6.5 or later, which implements proper countermeasures against electromagnetic side-channel analysis. Organizations should also consider additional physical security measures such as electromagnetic shielding, proper device placement, and regular security assessments to prevent exploitation. Implementing proper cryptographic side-channel resistance mechanisms, including constant-time implementations and randomization techniques, provides additional protection against similar vulnerabilities. The remediation process should include comprehensive testing of updated cryptographic implementations to ensure that the side-channel protections are properly functioning and that no regressions have been introduced in the cryptographic operations.