# CVE-2026-102946: joserfc: JWS signature verification bypass via empty signatures array in jws.deserialize_json

> Attackers can bypass JWS signature verification by providing an empty signatures array, allowing them to forge authenticated payloads in applications using joserfc.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Oct 2026
- **Updated:** 15 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-102946, GHSA-4pp3-559j-c5c2, UBUNTU-CVE-2026-102946, openSUSE-SU-2026:12204-1, openSUSE-SU-2026:22136-1

## What is CVE-2026-102946?

CVE-2026-102946 is a critical vulnerability in authlib joserfc, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.4, joserfc.jws.deserialize_json() accepts a JWS General JSON Serialization with an empty signatures array as authenticated. The verify_general_json() loop performs no iterations for the empty array and returns success because no signature check failed, allowing an attacker without a signing key to supply an arbitrary payload that relying applications may treat as authentic. The issue affects the General JSON Serialization path; compact JWS and JWT decoding, Flattened JSON serialization, and JWE JSON processing do not follow this vulnerable path. This issue is fixed in version 1.7.4.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-345 (Insufficient Verification of Data Authenticity), CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2026-102946?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `python-joserfc` | openSUSE:Leap 16.0 | All versions | 1.1.0-bp160.5.1 |
| `python-joserfc` | openSUSE:Tumbleweed | All versions | 1.7.7-1.1 |

## How do I fix CVE-2026-102946?

Upgrade to a fixed version.

## Is CVE-2026-102946 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-102946 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-102946 and fix it if it is affected.

What it is: CVE-2026-102946 is a critical vulnerability in authlib joserfc, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-102946 exists.

Affected product: authlib joserfc. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-102946/ (Markdown: https://insights.sbomify.com/CVE-2026-102946/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-102946
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-102946
- OSV: https://osv.dev/vulnerability/CVE-2026-102946

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-102946/
Summaries are generated and may contain mistakes; the official description above is the record.