# CVE-2026-65626: Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose


- **Severity:** Medium 5.9 (`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`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 26 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-65626, EEF-CVE-2026-65626, GHSA-vwvr-f994-6j9j, UBUNTU-CVE-2026-65626

## What is CVE-2026-65626?

CVE-2026-65626 is a medium-severity vulnerability in potatosalad jose, published on 26 Oct 2026. 

### Official description

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.

Weakness: CWE-203 (Observable Discrepancy)

## Which versions are affected by CVE-2026-65626?

1 open source package ship an affected version, including jose.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `jose` | Hex | From 1.3.0 | 1.11.13 |

## How do I fix CVE-2026-65626?

Upgrade jose to 1.11.13 or later.

## Is CVE-2026-65626 being exploited?

There is no known exploitation of CVE-2026-65626 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-65626 and fix it if it is affected.

What it is: CVE-2026-65626 is a medium-severity vulnerability in potatosalad jose, published on 26 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-65626 in the wild and no public exploit code.

Affected packages and fixed versions:
- jose (Hex): affected from 1.3.0; fixed in 1.11.13

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-65626/ (Markdown: https://insights.sbomify.com/CVE-2026-65626/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-65626
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-65626
- OSV: https://osv.dev/vulnerability/CVE-2026-65626

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-65626/
Summaries are generated and may contain mistakes; the official description above is the record.