---
title: "CVE-2026-102268: PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard"
url: https://erroneo.us/security/cve/CVE-2026-102268/
description: "CVE-2026-102268 (PyJWT (PyPI)): PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, ispemformat in jwt/utils.py is affected…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-28
date_modified: 2026-09-29
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-102268"
kev: false
cvss: 9.1
epss: 0.00202
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-102268: PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.2% , percentile 10: FIRST’s model estimates a 0.2% chance of exploitation activity in the next 30 days, higher than 10% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes PyJWT (PyPI) <= 2.13.0, fixed in 2.14.0 . Check your lockfile, including transitive dependencies.

## What it is

PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, ispemformat in jwt/utils.py is affected because ispemformat does not recognize every PEM representation accepted by the cryptography loader. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a mutated public-key PEM as raw key bytes. As a result, HMACAlgorithm.preparekey treats the unrecognized asymmetric public key as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.

## Affected packages

- PyPI `PyJWT` <= 2.13.0 → fixed: 2.14.0

## Affected products (CVE record)

- jpadilla pyjwt: < 2.14.0

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.20% probability of exploitation activity in the next 30 days; percentile 10.

## Sources

- [GitHub Advisory GHSA-ffc3-869f-jxw9](https://github.com/advisories/GHSA-ffc3-869f-jxw9)
- [CVE.org record CVE-2026-102268](https://www.cve.org/CVERecord?id=CVE-2026-102268)
- [NVD entry CVE-2026-102268](https://nvd.nist.gov/vuln/detail/CVE-2026-102268)
- [github.com](https://github.com/jpadilla/pyjwt/security/advisories/GHSA-ffc3-869f-jxw9)
- [github.com](https://github.com/jpadilla/pyjwt/commit/8b4e233a22206b34ec1186e912e75c0b2396ac07)
- [github.com](https://github.com/jpadilla/pyjwt/releases/tag/2.14.0)

---
Source page: https://erroneo.us/security/cve/CVE-2026-102268/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt