# CVE-2026-65625: Attacker-controlled AES-GCM authentication tag length allows tag forgery in jose


- **Severity:** Medium 5.9 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/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-2026-65625, EEF-CVE-2026-65625, GHSA-6gxw-6f7r-cjr6, UBUNTU-CVE-2026-65625

## What is CVE-2026-65625?

CVE-2026-65625 is a medium-severity vulnerability in potatosalad jose, published on 26 Oct 2026. 

### Official description

The pure-Erlang AES-GCM fallback in jose_jwa_aes derives the number of verified authentication tag bits from the attacker-supplied tag itself. In the {aes_gcm, Bits} clause of block_decrypt/4, the incoming tag is guarded only by is_binary/1, with no check on its length. Verification in gcm_block_decrypt/6 then computes TBits = bit_size(T) and compares only those bits of the real 128-bit tag. An attacker who controls a JWE token can truncate the authentication tag to as little as 8 bits, so only 8 bits are ever checked. This reduces forgery resistance from 2^-128 to 2^-8, and a forged ciphertext is reliably accepted as authentic within 256 attempts without knowledge of the key (an authentication tag forgery and integrity bypass). Supplying a tag longer than 128 bits instead causes a badmatch that crashes the decrypting process. The fallback is reached through the public JWE decryption path whenever AES-GCM is not provided by a native crypto NIF, for example on FIPS or stripped or older OTP builds.

This issue affects jose: from 1.2.0 before 1.11.13.

Weakness: CWE-354 (Improper Validation of Integrity Check Value)

## Which versions are affected by CVE-2026-65625?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `jose` | Hex | From 1.2.0 | 1.11.13 |

## How do I fix CVE-2026-65625?

Upgrade jose to 1.11.13 or later.

## Is CVE-2026-65625 being exploited?

There is no known exploitation of CVE-2026-65625 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-65625 and fix it if it is affected.

What it is: CVE-2026-65625 is a medium-severity vulnerability in potatosalad jose, published on 26 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-65625 in the wild and no public exploit code.

Affected packages and fixed versions:
- jose (Hex): affected from 1.2.0; 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-2026-65625/ (Markdown: https://insights.sbomify.com/CVE-2026-65625/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-65625
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-65625
- OSV: https://osv.dev/vulnerability/CVE-2026-65625

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-65625/
Summaries are generated and may contain mistakes; the official description above is the record.