Vulnerability Overview CVE-2025-66442 - Compiler-Induced Constant-Time Violation Modern versions of the Clang compiler, when LLVM's optimization feature is enabled, introduce timing side channels in padding verification code on certain platforms. This optimization transforms originally constant-time code branches into non-constant-time equivalent code, allowing attackers to conduct padding oracle attacks through precise timing measurements to decrypt target ciphertexts. Core Issue: Compiler optimizations break carefully written constant-time protection code in cryptographic libraries, causing padding verification timing to depend on secret data. --- Affected Scope Specific Vulnerable Functions: RSA-PKCS#1 v1.5 decryption One-and-zeros depadding ( ) Attack Impact: Attackers can submit chosen ciphertexts and recover ciphertext contents (not the key) by precisely measuring decryption timing. --- Remediation Temporary Mitigation Measures Use Clang default optimization levels ( or lower, such as , ) Avoid advanced compiler optimization options, particularly Prefer AEAD modes over CBC mode, and RSA-OAEP over PKCS#1v1.5 Official Fix Affected users should recompile, disabling the LLVM option and using only default optimization flags (such as or ) > ⚠️ Current Status: No fix is available at this time