---
id: CVE-2026-89086
title: >-
  In the jose package before 0.11.0 for OCaml, library calls to validate an RSA
  signature only confirm that PKCS #1 decoding succeeds, and proceed to declare
  the signature valid without the required steps that involve the public key.
summary: >-
  In the jose package before 0.11.0 for OCaml, library calls to validate an RSA
  signature only confirm that PKCS #1 decoding succeeds, and proceed to declare
  the signature valid without the required steps that involve the public key.
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-347
vendor: OCaml
product: jose
affected:
  - jose < 0.11.0
published: '2026-09-10'
updated: '2026-09-22'
sourceUpdated: '2026-09-22T20:00:03.713'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89086'
references:
  - url: >-
      https://github.com/ulrikstrid/ocaml-jose/commit/cf17d991ec6a0d1997956b6c7799890f9c28879e
    label: cve@mitre.org
  - url: 'https://osv.dev/vulnerability/OSEC-2026-19'
    label: cve@mitre.org
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.00198
epssPercentile: 0.09914
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-09-10T20:40:09.935199Z'
ingestedAt: '2026-09-14T14:09:30.520Z'
---

## Overview

In the jose package before 0.11.0 for OCaml, library calls to validate an RSA signature only confirm that PKCS #1 decoding succeeds, and proceed to declare the signature valid without the required steps that involve the public key.

## Remediation

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