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CVE-2026-65630— Timing side-channel in pure-Erlang X25519 scalar multiplication leaks the private key in jose

Quick assessment

Affected

potatosalad jose

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

potatosalad jose 中存在“可观测时序差异”漏洞，攻击者可通过纯 Erlang 实现的 Curve25519 回退路径中的时序侧信道，恢复长期使用的 X25519 私钥。该纯 Erlang 版本的 X25519 实现，在利用递归 Montgomery 阶梯（）对秘密私钥执行标量乘法时，其子句会根据经钳位（clamped）的私有标量的各个比特位进行分支；且其每一步操作（与）以及域逆运算，均基于依赖具体数值的 Erlang 大整数算术（包括乘法、取余和模幂运算）。尽管该阶梯在操作次数上保持平衡并固

CVSS 5.9 · Medium Updated Oct 27, 2026

Possible ATT&CK Techniques 2 AI

T1059.001 · PowerShell T1190 · Exploit Public-Facing Application

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Vulnerability Information

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Vulnerability Title

Timing side-channel in pure-Erlang X25519 scalar multiplication leaks the private key in jose

Source: CVE Program / CVE List V5

Vulnerability Description

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.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Source: CVE Program / CVE List V5

Vulnerability Type

通过时间差异性导致的信息暴露

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
potatosalad	jose	1.10.0 ~ 1.11.13	`cpe:2.3:a:potatosalad:jose::::::::`
potatosalad	jose	8e532095de114ef4bf88a9ec5d651fa251a972b3 ~ 3670f873c274bba86fb7f5ee5727a7efa1322b79	`cpe:2.3:a:potatosalad:jose::::::::`

II. Public POCs for CVE-2026-65630

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-65630

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Patches & Fixes for CVE-2026-65630 (1)

🔗 Prepare 1.11.13 security candidate and public API regressions · potatosalad/erlang-jose@3670f87 · GitHub Read full article patch

Vendor Advisories for CVE-2026-65630 (3)

🔗 Non-constant-time scalar multiplication leaks the private scalar · Advisory · potatosalad/erlang-jose · GitHub Read full article vendor-advisory related
🔗 EEF-CVE-2026-65630 - OSV related
🔗 CVE-2026-65630 Read full article related

https://www.cve.org/CVERecord?id=CVE-2026-65630

Same Patch Batch · potatosalad · 2026-10-26 · 8 CVEs total

CVE-2026-65629	7.4 HIGH	Weak PBKDF2 parameters for password-encrypted private-key export in jose
CVE-2026-65627	6.9 MEDIUM	Decompression bomb via unbounded zlib:inflate in jose_jwe_zip:uncompress/2
CVE-2026-65631	6.9 MEDIUM	erlang-jose RSA JWK parsing attempts to factor an attacker-controlled modulus, enabling CP
CVE-2026-65626	5.9 MEDIUM	Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose
CVE-2026-65628	5.9 MEDIUM	Infinite recursion (CPU denial-of-service) in JOSE.JWK.shared_secret/2 on mismatched key t
CVE-2026-65625	5.9 MEDIUM	Attacker-controlled AES-GCM authentication tag length allows tag forgery in jose
CVE-2026-65632	5.1 MEDIUM	ECDSA signature length is not validated in jose, allowing signature malleability

IV. Related Vulnerabilities

Same product: jose

Same vendor: potatosalad

Same weakness: CWE-208