Threats Tagged 'cve-2026-18040'

Bouncy Castle for Java versions before 1.86 contain side-channel vulnerabilities in the HQC implementation. These vulnerabilities arise from the use of lookup tables in GF(2^8) arithmetic and a fixed-weight support sampler that leaks secret-derived data through cache timing and branch behavior. An attacker observing cache or timing behavior during encapsulation or decapsulation could potentially recover information about the HQC private key. The vulnerabilities have been addressed by removing table lookups and making the sampler branch-free within candidate batches.

CVE-2026-18040 is a medium severity vulnerability in Bouncy Castle for Java versions 1.73 up to but not including 1.86. It involves observable timing and cache side channels in the HQC cryptographic implementation, which leak secret-derived data during encapsulation and decapsulation. The flaw arises from lookup tables used in GF(2^8) arithmetic and a fixed-weight support sampler that reveals secret indices through timing differences. These side channels can allow an attacker with the ability to observe cache behavior or timing to gain information about the private key. The vulnerability has been addressed by removing table lookups and making the sampler branch-free, preserving output and randomness consumption.