---
id: CVE-2026-65631
title: >-
  erlang-jose RSA JWK parsing attempts to factor an attacker-controlled modulus,
  enabling CPU-exhaustion denial of service
summary: >-
  Inefficient Algorithmic Complexity in erlang-jose allows an unauthenticated
  remote attacker to cause a CPU-exhaustion denial of service by submitting a
  crafted RSA JSON Web Key.


  When an application parses an untrusted JWK through the pu…
severity: medium
cvss: 6.9
cvssVector: 'CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-407
vendor: potatosalad
product: jose
affected:
  - jose >= 1.7.7 < 1.11.13
  - >-
    potatosalad/erlang-jose >= d19e1ba68d88c68d29aa942be2573a22dbafca1f <
    bfd336c0062bff93e65d08c22361897e96afd956
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T19:53:45.204Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-65631'
references:
  - url: >-
      https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-3m45-vrpj-xmrq
  - url: 'https://cna.erlef.org/cves/CVE-2026-65631.html'
    label: EEF CNA record for CVE-2026-65631
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-65631'
    label: OSV record EEF-CVE-2026-65631
  - url: >-
      https://github.com/potatosalad/erlang-jose/commit/d19e1ba68d88c68d29aa942be2573a22dbafca1f
    label: Introducing commit d19e1ba in potatosalad/erlang-jose
  - url: >-
      https://github.com/potatosalad/erlang-jose/commit/bfd336c0062bff93e65d08c22361897e96afd956
    label: Fix commit bfd336c in potatosalad/erlang-jose
tags:
  - cve.org
ingestedAt: '2026-10-26T20:39:42.625Z'
epss: 0.00235
epssPercentile: 0.14301
---

## Overview

Inefficient Algorithmic Complexity in erlang-jose allows an unauthenticated remote attacker to cause a CPU-exhaustion denial of service by submitting a crafted RSA JSON Web Key.

When an application parses an untrusted JWK through the public jose_jwk:from_binary/1 or jose_jwk:from_map/1 API (or the Elixir wrappers JOSE.JWK.from_binary/1 and JOSE.JWK.from_map/1), an RSA private key that supplies d, e, and n but omits all Chinese Remainder Theorem parameters (p, q, dp, dq, qi) is routed into convert_sfm_to_crt/1, which tries to recover the missing primes by factoring the modulus. The three integers are read straight from the base64url input and are never validated as a real RSA key. When the modulus cannot be split into two factors (for example, when it is itself prime), the search loop convert_sfm_to_crt_find_p/6 performs a modular exponentiation over the attacker-sized modulus on every iteration and never succeeds. A single request of a few hundred bytes forces close to one CPU-second of work before an internal one-second watchdog kills the worker, and a larger modulus raises the cost further. By flooding such requests an attacker can saturate every scheduler and deny service, without credentials, a valid RSA key, or any special configuration.

This issue affects jose: from 1.7.7 before 1.11.13.

## Affected

- `jose >= 1.7.7 < 1.11.13`
- `potatosalad/erlang-jose >= d19e1ba68d88c68d29aa942be2573a22dbafca1f < bfd336c0062bff93e65d08c22361897e96afd956`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.