# CVE-2026-102270: PyJWT: ReDoS vulnerability when calling the `is_pem_format` function.

CVE-2026-102270 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-102270, released October 4, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-102270
- Priority: Routine
- CVSS: 4.9 (Moderate)
- EPSS: 0.0025
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 28, 2026
- Weakness: Inefficient Regular Expression Complexity
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-102270

## Description

PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, PyJWT is_pem_format is affected because lazy PEM regular expression backtracks extensively. This occurs when a certificate-like input contains repeated BEGIN markers without a matching END marker. As a result, is_pem_format performs unbounded backtracking while searching for a PEM end marker. Consequently, an attacker can cause intensive CPU consumption. This issue is fixed in version 2.14.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | pyjwt Debian 14 | 2.14.0-1 | [DEBIAN-CVE-2026-102270](https://patchblox.com/security/data/fix/linux/debian-cve-2026-102270.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 |

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Data as of 2026-11-10T01:44:33Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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