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

Source: https://junglewise.ai/threats/cve-2026-65626-the-pure-erlang-rsaes-pkcs1-v1-5-decryption-in-the-jose-jwa-pkcs1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-26. Updated: 2026-10-26  
License: CC BY 4.0 with a link back

CVE-2026-65626 · Severity: info · Published 2026-10-26

The jose Erlang library implements RSA decryption using a vulnerable algorithm that leaks information about whether padding is valid, allowing attackers to decrypt messages without the private key. An attacker who can send encrypted data to a decryption endpoint can recover sensitive keys and encrypted content through thousands of carefully crafted queries, potentially exposing encrypted communications or enabling signature forgery.

Technologies: [JOSE](https://junglewise.ai/threats/technologies/jose-jose). Vendors: [Jose](https://junglewise.ai/threats/vendors/jose).

## Quick answers

**Is CVE-2026-65626 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-65626 being exploited in the wild.

**How severe is CVE-2026-65626?** Informational severity, published 26 October 2026.

**Which products and versions are affected?** JOSE 1.3.0 to before 1.11.13.

**Is there a fix for CVE-2026-65626?** Yes: fixed in 1.11.13. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-65626 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-65626?** Check whether you run JOSE at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 1.11.13

## Technical details

The vulnerable eme_pkcs1_decode/2 function in jose_jwa_pkcs1 returns distinct error responses for valid versus invalid PKCS#1 v1.5 padding, creating a padding oracle. Combined with unblinded RSA decryption in dp/2, this leaks both a one-bit padding-conformance signal and timing information. An unauthenticated attacker with network access to RSA1_5 JWE decryption endpoints can exploit this through chosen-ciphertext attacks requiring 10^4 to 10^6 queries to recover plaintext.

## Affected products

- jose jose 1.3.0 to before 1.11.13

## Timeline

- 2026-10-26: disclosed

## References

- [https://repo.hex.pm/](https://repo.hex.pm/)
- [https://github.com/](https://github.com/)

## Related threats

- [JOSE library weak password hashing in encrypted key export](https://junglewise.ai/threats/cve-2026-65629-use-of-password-hash-with-insufficient-computational-effort-in)
- [jose AES-GCM authentication tag truncation in fallback](https://junglewise.ai/threats/cve-2026-65625-the-pure-erlang-aes-gcm-fallback-in-jose-jwa-aes-derives-the)