# CVE-2026-101918: PyJWT: Unauthenticated RecursionError DoS in pre-verification payload parse (PyJWKClient.get_signing_key_from_jwt / verify_signature=False)

CVE-2026-101918 is fixed in 5 products on 1 platform, first by python3-jwt 2.10.1-4ubuntu1.3, released September 28, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-101918
- Priority: High
- CVSS: 7.5 (Moderate)
- EPSS: 0.0041
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 28, 2026
- Weakness: Uncaught Exception
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-101918

## Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.0.0a1 until 2.15.0, PyJWT PyJWKClient.get_signing_key_from_jwt is affected because payload parser catches ValueError but not RecursionError. This occurs when an attacker-controlled recursively nested payload reaches json.loads. As a result, documented PyJWT exception handling does not contain the failure. Consequently, an unauthenticated request can raise an exception that may produce an HTTP 500 response. The advisory-defined affected implementation also includes jwt/api_jwt.py, verify_signature=False. This issue is fixed in version 2.15.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | pyjwt Debian 14 | 2.15.0-1 | [DEBIAN-CVE-2026-101918](https://patchblox.com/security/data/fix/linux/debian-cve-2026-101918.md) | Oct 4, 2026 |
| Linux | python-PyJWT opensuse-leap 16.0 | 2.12.1-160000.3.1 | [OPENSUSE-SU-2026:22074-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22074-1.md) | Nov 7, 2026 |
| Linux | python-PyJWT sles 15.6 | 2.8.0-150400.8.20.1 | [SUSE-SU-2026:5064-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5064-1.md) | Nov 7, 2026 |
| Linux | python-PyJWT sles 15.7 | 2.8.0-150400.8.20.1 | [SUSE-SU-2026:5064-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5064-1.md) | Nov 7, 2026 |
| Linux | python-PyJWT sles 16.0 | 2.12.1-160000.3.1 | [SUSE-SU-2026:24219-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24219-1.md) | Nov 7, 2026 |
| Linux | python-jwt Ubuntu 18.04.6 LTS (bionic) | 1.5.3+ds1-1ubuntu0.1+esm4 | [python-jwt 1.5.3+ds1-1ubuntu0.1+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-python-jwt-1.5.3-ds1-1ubuntu0.1-esm4.md) | Oct 27, 2026 |
| Linux | python3-jwt Ubuntu 18.04.6 LTS (bionic) | 1.5.3+ds1-1ubuntu0.1+esm4 | [python3-jwt 1.5.3+ds1-1ubuntu0.1+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-python3-jwt-1.5.3-ds1-1ubuntu0.1-esm4.md) | Oct 27, 2026 |
| Linux | python3-jwt Ubuntu 20.04 LTS (focal) | 1.7.1-2ubuntu2.1+esm4 | [python3-jwt 1.7.1-2ubuntu2.1+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-focal-python3-jwt-1.7.1-2ubuntu2.1-esm4.md) | Oct 27, 2026 |
| Linux | python3-jwt Ubuntu 22.04.1 LTS (jammy) | 2.3.0-1ubuntu0.6 | [python3-jwt 2.3.0-1ubuntu0.6](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-python3-jwt-2.3.0-1ubuntu0.6.md) | Oct 27, 2026 |
| Linux | python3-jwt Ubuntu 24.04.5 LTS (noble) | 2.7.0-1ubuntu0.4 | [python3-jwt 2.7.0-1ubuntu0.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-jwt-2.7.0-1ubuntu0.4.md) | Oct 27, 2026 |
| Linux | python3-jwt Ubuntu 26.04.1 LTS (resolute) | 2.10.1-4ubuntu1.3 | [python3-jwt 2.10.1-4ubuntu1.3](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-python3-jwt-2.10.1-4ubuntu1.3.md) | Sep 28, 2026 |
| Linux | python3-jwt amzn 2023 | 2.4.0-1.amzn2023.0.6 | [ALAS2023-2026-3298](https://patchblox.com/security/data/fix/linux/alas2023-2026-3298.md) | Nov 7, 2026 |
| Linux | python3-jwt+crypto amzn 2023 | 2.4.0-1.amzn2023.0.6 | [ALAS2023-2026-3298](https://patchblox.com/security/data/fix/linux/alas2023-2026-3298.md) | Nov 7, 2026 |

---

Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.