Observable Timing Discrepancy vulnerability in potatosalad jose allows recovery of a long-term X25519 private key through a timing side…

Observable Timing Discrepancy vulnerability in potatosalad jose allows recovery of a long-term X25519 private key through a timing side channel in the pure-Erlang Curve25519 fallback. The pure-Erlang X25519 implementation performs scalar multiplication over the secret private key using a recursive Montgomery ladder (josejwax25519:curve25519/2) whose clauses branch on individual bits of the clamped private scalar, and whose per-step operations (josejwax25519:montgomeryadd/3 and josejwax25519:montgomerydouble/1) and field inversion are built from value-dependent Erlang bignum arithmetic (multiplication, remainder, and modular exponentiation). Although the ladder is operation-count balanced and fixed at 254 steps, the concrete integer values processed at each step, and therefore the running time, depend on the secret scalar. The execution time of the public entry points josejwax25519:scalarmult/2, josejwax25519:x25519/2, josejwax25519:x25519base/1, and josejwax25519:sktopk/1 is thus a function of the private key. This path is reachable from the public API, most notably when a service decrypts attacker-supplied ECDH-ES (JWE) messages with a long-term X25519 key (for example through…

curl https://cve.zerocrew.in/api/cve/CVE-2026-65630