# CVE-2026-65625: jose AES-GCM authentication tag truncation in fallback

Source: https://junglewise.ai/threats/cve-2026-65625-the-pure-erlang-aes-gcm-fallback-in-jose-jwa-aes-derives-the  
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-2026-65625 · Severity: info · Published 2026-10-26

jose is a JWT/JWE library that provides encrypted JSON Web Encryption tokens. The pure-Erlang AES-GCM fallback used when native crypto is unavailable accepts truncated authentication tags, allowing an attacker to forge valid tokens by reducing verification strength from 2^-128 to 2^-8. This can lead to account takeover or data access if JWE tokens are used for authentication or sensitive operations.

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

## Quick answers

**Is CVE-2026-65625 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-65625 being exploited in the wild.

**How severe is CVE-2026-65625?** Informational severity, published 26 October 2026.

**Which products and versions are affected?** JOSE 1.2.0 to before 1.11.13.

**Is there a fix for CVE-2026-65625?** Yes: fixed in jose 1.11.13. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-65625 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-65625?** 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 jose 1.11.13

## Technical details

The vulnerability exists in the pure-Erlang AES-GCM fallback implementation (jose_jwa_aes), where the block_decrypt/4 function derives the number of bits to verify from the attacker-supplied authentication tag length rather than enforcing the standard 128-bit requirement. An attacker can truncate a JWE token's authentication tag to as few as 8 bits, reducing forgery resistance to 2^-8, allowing reliable token forgery within ~256 attempts without key knowledge.

## Affected products

- jose jose 1.2.0 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 RSAES-PKCS1-v1_5 Bleichenbacher padding oracle](https://junglewise.ai/threats/cve-2026-65626-the-pure-erlang-rsaes-pkcs1-v1-5-decryption-in-the-jose-jwa-pkcs1)