CVE Intelligence
Medium

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

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.

Published Oct 26, 2026 · Updated Oct 26, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database · CNA: EEF

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
—
No EPSS score.
Affects
Potatosalad
Jose
CVSS base
5.9
Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Potatosalad Jose).
  2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  3. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Potatosalad Jose ≥ 1.10.0 and < 1.11.13≥ 8e532095de114ef4bf88a9ec5d651fa251a972b3 and < 3670f873c274bba86fb7f5ee5727a7efa1322b79 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
High
Attack requirements
Present
Privileges required
None
User interaction
None
Scope
X
Confidentiality (vulnerable system)
High
Integrity (vulnerable system)
None
Availability (vulnerable system)
None
Confidentiality (subsequent)
None
Integrity (subsequent)
None
Availability (subsequent)
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.9 CVSS 4.0 Medium — — 6b3ad84c-e1a6-4bf7-a703-f496b71e49db via NIST National Vulnerability Database
5.9 CVSS 4.0 Medium — — EEF via CVE Program (cve.org) e CISA ADP
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X (score shown at the top: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-208

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

  • 2026
  • Source status changed · Published → Received
    Oct 26, 2026 · NIST National Vulnerability Database
  • Record published
    Oct 26, 2026
  • CVSS changed · 5.9
    Oct 26, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · → Published
    Oct 26, 2026 · CVE Program (cve.org) e CISA ADP
  • Record created in this database
    Oct 26, 2026 · CVE Program (cve.org) e CISA ADP
  • CVE published
    Oct 26, 2026 · EEF

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 26, 2026 – Oct 26, 2026

References

5 on the record

Elsewhere on this site

Potatosalad
every CVE for this vendor
CWE-208
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-65632 ECDSA signature length is not validated in jose, allowing signature malleability 5h
  • CVE-2026-65626 Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose 5h
  • CVE-2026-65627 Decompression bomb via unbounded zlib:inflate in jose_jwe_zip:uncompress/2 5h
  • CVE-2026-65628 Infinite recursion (CPU denial-of-service) in JOSE.JWK.shared_secret/2 on mismatched key types 5h
  • CVE-2026-65629 Weak PBKDF2 parameters for password-encrypted private-key export in jose 5h
  • CVE-2026-65631 erlang-jose RSA JWK parsing attempts to factor an attacker-controlled modulus, enabling CPU-exhaustion denial of service 5h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No FIRST EPSS score.
  • No fixed version, patch or mitigation documented.
  • No CISA SSVC assessment.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-65630 is "Timing side-channel in pure-Erlang X25519 scalar multiplication leaks the private key in jose", rated Medium. It affects Jose (Potatosalad); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.9 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.

Sign in or create an account to comment and suggest corrections.