# CVE-2026-102268: PyJWT HMAC signature forgery via PEM parsing bypass

Source: https://junglewise.ai/threats/cve-2026-102268-pyjwt-is-a-python-implementation-of-json-web-token-standards  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-28. Updated: 2026-09-28  
License: CC BY 4.0 with a link back

CVE-2026-102268 · Severity: critical · CVSS 9.1 · Published 2026-09-28

PyJWT is a Python library used to create and validate JSON Web Tokens (JWTs), a common method for securing API authentication and session management. An attacker who knows the public key can forge valid authentication tokens if the application mixes HMAC and asymmetric signing algorithms, allowing unauthorized access to protected resources or impersonation of legitimate users.

Technologies: [pyjwt (PyPI)](https://junglewise.ai/threats/technologies/pypi-pyjwt). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-102268 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102268 being exploited in the wild.

**How severe is CVE-2026-102268?** Critical severity, with a CVSS score of 9.1, published 28 September 2026.

**Which products and versions are affected?** PyJWT Project PyJWT prior to 2.14.0; pyjwt (PyPI) <= 2.13.0, ECOSYSTEM:introduced=0,fixed=2.14.0.

**Is there a fix for CVE-2026-102268?** Yes. pyjwt (PyPI): upgrade to 2.14.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-102268 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-102268?** Check whether you run PyJWT Project PyJWT or pyjwt (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- pyjwt (PyPI): upgrade to 2.14.0 or later

  ```sh
  pip install "pyjwt>=2.14.0"
  ```


## Technical details

The is_pem_format function in jwt/utils.py fails to recognize certain PEM representations that are accepted by the cryptography library's key loader. When an application supplies a mutated public-key PEM as raw bytes alongside HMAC algorithm support, the library incorrectly treats the asymmetric key as an HMAC secret. An attacker with knowledge of the public key can then forge valid HMAC-signed tokens. The vulnerability requires the application to mix HMAC and asymmetric algorithms and was patched in version 2.14.0.

## Affected products

- PyJWT Project PyJWT prior to 2.14.0

## Identifiers

- CVE-2026-102268
- GHSA-ffc3-869f-jxw9
- PYSEC-2026-4145

## Timeline

- 2026-09-28: disclosed
- 2026-09: patched: Version 2.14.0 released

## References

- [https://github.com/jpadilla/pyjwt/commit/8b4e233a22206b34ec1186e912e75c0b2396ac07](https://github.com/jpadilla/pyjwt/commit/8b4e233a22206b34ec1186e912e75c0b2396ac07)
- [https://github.com/jpadilla/pyjwt/releases/tag/2.14.0](https://github.com/jpadilla/pyjwt/releases/tag/2.14.0)

## Related threats

- [PyJWT HS256/384/512 token forgery via empty HMAC key in oct JWK](https://junglewise.ai/threats/pyjwt-hs256-384-512-verify-accepts-empty-hmac-key-via-oct-jwk-pyjwk-a3ba63d2)
- [PyJWT decode() options-dict mutation enabling claim-verification bypass](https://junglewise.ai/threats/cve-2026-103001-pyjwt-decode-reintroduces-options-dict-mutation-enabling-silent)
- [PyJWT OKP algorithm key validation bypass](https://junglewise.ai/threats/cve-2026-102275-pyjwt-is-a-python-implementation-of-json-web-token-standards)
- [PyJWT unhandled ValueError in JWK Set parsing](https://junglewise.ai/threats/cve-2026-102274-pyjwt-is-a-python-implementation-of-json-web-token-standards)
- [PyJWT HMAC key validation bypass in HMACAlgorithm.prepare_key](https://junglewise.ai/threats/cve-2026-102273-pyjwt-is-a-python-implementation-of-json-web-token-standards)