PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard — GHSA-FFC3-869F-JXW9

Summary

**Prerequisites** (both conditions must hold; both are deployment properties, not attacker-controlled at request time): - The `jwt.decode` allow-list mixes an HMAC algorithm with an asymmetric one, e.g. `algorithms=["ES256", "HS256"]` (the RFC 8725 footgun the guard exists to backstop). - The verification key is passed as raw PEM text/bytes on the non-`PyJWK` path, in a byte-form that `cryptography`'s loader…

Timeline

Published by source

2026-09-29

Risk context

• Reported severity or threat level: critical.
• Reported CVSS score: 9.1 out of 10.
• Reported EPSS value: 0.00196.
• Review exposure for the affected product or family: pip: PyJWT.

Product

pip: PyJWT

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-FFC3-869F-JXW9

Source

GitHub

Vendor

GitHub

Published by source

2026-09-29

Last source activity

2026-09-29

Additional identifiers

CVE-2026-102268

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.