---
id: CVE-2026-65626
title: Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose
summary: >-
  The pure-Erlang RSAES-PKCS1-v1_5 decryption in the jose_jwa_pkcs1 module is a
  Bleichenbacher padding oracle. eme_pkcs1_decode/2 returns the recovered
  message when a decrypted block has valid PKCS#1 v1.5 padding (a leading 0x00
  0x02, a pa…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-203
vendor: potatosalad
product: jose
affected:
  - jose >= 1.3.0 < 1.11.13
  - >-
    potatosalad/erlang-jose >= 853c5d4c4c0bd2a7ecb055b237f4284184e176c8 <
    0eac8cef9aaa48fb6846f4e47a0002dc4a73966d
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T19:53:05.620Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-65626'
references:
  - url: >-
      https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-vwvr-f994-6j9j
  - url: 'https://cna.erlef.org/cves/CVE-2026-65626.html'
    label: EEF CNA record for CVE-2026-65626
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-65626'
    label: OSV record EEF-CVE-2026-65626
  - url: >-
      https://github.com/potatosalad/erlang-jose/commit/853c5d4c4c0bd2a7ecb055b237f4284184e176c8
    label: Introducing commit 853c5d4 in potatosalad/erlang-jose
  - url: >-
      https://github.com/potatosalad/erlang-jose/commit/0eac8cef9aaa48fb6846f4e47a0002dc4a73966d
    label: Fix commit 0eac8ce in potatosalad/erlang-jose
tags:
  - cve.org
ingestedAt: '2026-10-26T20:39:42.627Z'
epss: 0.00092
epssPercentile: 0.00497
---

## Overview

The pure-Erlang RSAES-PKCS1-v1_5 decryption in the jose_jwa_pkcs1 module is a Bleichenbacher padding oracle. eme_pkcs1_decode/2 returns the recovered message when a decrypted block has valid PKCS#1 v1.5 padding (a leading 0x00 0x02, a padding string of at least eight non-zero bytes, and a 0x00 separator) and returns a distinct error result otherwise, and rsaes_pkcs1_decrypt/2 additionally returns {error, {badsize, _}} when the length check fails. The implementation applies no implicit-rejection countermeasure (RFC 8017 §7.2.2): it does not substitute a deterministic pseudo-random plaintext on a padding failure, so a one-bit padding-conformance signal leaks to the caller. Because the underlying modular exponentiation in dp/2 is a raw, non-blinded crypto:mod_pow/3, the padding check also stays distinguishable by timing even when an application normalizes every failure to a single error value.

An unauthenticated attacker who knows only the public RSA key and can submit ciphertexts to a decryption endpoint that unwraps RSA1_5 JWE keys (or otherwise calls decrypt_private/3 with rsa_pkcs1_padding) can use this oracle to recover the plaintext of intercepted ciphertexts, such as content-encryption keys and thus the protected message, or to forge signatures, through roughly 10^4 to 10^6 adaptive chosen-ciphertext queries.

This issue affects jose: from 1.3.0 before 1.11.13.

## Affected

- `jose >= 1.3.0 < 1.11.13`
- `potatosalad/erlang-jose >= 853c5d4c4c0bd2a7ecb055b237f4284184e176c8 < 0eac8cef9aaa48fb6846f4e47a0002dc4a73966d`

## Remediation

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