Live › vulnerability › CVE-2026-65630
Go to dashboardThe pure-Erlang X25519 fallback in the jose library runs time that depends on the secret scalar, so the running time leaks the private key bit by bit. An attacker who can submit ECDH-ES JWE ciphertexts to a service decrypting with a long-term X25519 key and measure timing could in principle recover that key.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-26 20:50 UTC. All times on this page are UTC.
Services that use the jose library from 1.10.0 up to but not including 1.11.13 and decrypt attacker-supplied ECDH-ES JWE messages with a long-term X25519 key, where the pure-Erlang fallback is used. Systems that only sign, only use other key types, or never receive attacker-controlled ciphertexts are unlikely to be exposed.
No product ranges from the sources yet.
rebar.lock or mix.lock) and see whether it is 1.10.0 or later but before 1.11.13.JOSE.JWK.box_decrypt_ecdh_es/2 or jose_jwa_x25519 with a long-term X25519 key.1.11.13 or later.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
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 (jose_jwa_x25519:curve25519/2) whose clauses branch on individual bits of the clamped private scalar, and whose per-step operations (jose_jwa_x25519:montgomery_add/3 and jose_jwa_x25519:montgomery_double/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 jose_jwa_x25519:scalarmult/2, jose_jwa_x25519:x25519/2, jose_jwa_x25519:x25519_base/1, and jose_jwa_x25519:sk_to_pk/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 JOSE.JWK.box_decrypt_ecdh_es/2, which reaches jose_jwa_curve25519:x25519_shared_secret/2 and the ladder). An attacker who can submit ciphertexts and measure decryption timing can, in principle, recover the private key bit by bit, defeating the resistance X25519 was designed to provide. Recovery of the key compromises the confidentiality and authenticity of all data protected by it.
This issue affects jose: from 1.10.0 before 1.11.13.
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