In the Linux kernel, the following vulnerability has been resolved: crypto: ecc - Fix carry overflow in vli multiplication The carry flag calculation fails when r01.m_high is saturated (0xFFFFFFFFFFFFFFFF) and addition of lower bits overflows. The condition (r01.m_high < product.m_high) doesn't handle the case where r01.m_high == product.m_high and an additional carry exists from lower-bit overflow. When commit 3c4b23901a0c ("crypto: ecdh - Add ECDH software support") introduced crypto/ecc.c, it split the muladd() function in the micro-ecc library into separate mul_64_64() and add_128_128() helpers. It seems the check got lost in translation. Add proper handling for this boundary by accounting for the carry from the lower addition.
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This CVE exploits attack patterns that Casky's 0matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.
CVE-2026-64313 is a cryptographic implementation vulnerability in the Linux kernel's elliptic curve cryptography (ECC) library that affects carry flag calculation during multiplication operations. The flaw occurs in crypto/ecc.c when the carry flag fails to properly detect overflow conditions, specifically when the high bits are saturated (0xFFFFFFFFFFFFFFFF) and additional carries propagate from lower-bit arithmetic. This vulnerability impacts any system relying on kernel-based ECDH key exchange for cryptographic operations, including TLS/SSL connections, VPN implementations, and secure boot mechanisms. Threat actors could potentially exploit this to weaken or break elliptic curve cryptography protections, compromising confidentiality and integrity of encrypted communications.
While Casky currently shows zero matching skills for this specific CVE, practitioners using Casky's Claude AI-powered analysis would typically monitor for patterns associated with Cryptography (T1573) and Data Encrypted for Impact (T1486) MITRE ATT&CK techniques, as successful exploitation could lead to weakened encryption or key derivation attacks. Extended reasoning analysis would focus on kernel-level code paths handling cryptographic operations, identifying suspicious mathematical anomalies in multiplication routines and unexpected cryptographic failures during key negotiation. Security teams should prioritize patching Linux systems, particularly those handling sensitive cryptographic operations, and monitor for CVE-2026-64313 exploitation indicators as the vulnerability details become more widely known in threat intelligence feeds.
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