PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation (CVE-2026-102266) | HOL Guard CVE

High · CVSS 7.4CVE-2026-102266

PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation

Answer in brief

CVE-2026-102266 records a High severity (CVSS 7.4) vulnerability in PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation. The current sources do not mark it as known exploited. The current feed maps jpadilla/pyjwt (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 28, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 28, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.4
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.4. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps jpadilla/pyjwt (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
jpadilla/pyjwtgeneric	>=2.13.0 <2.14.0	2.14.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for jpadilla/pyjwt.
Review the reported fix. Update jpadilla/pyjwt to 2.14.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 28, 2026

Sources and claim methodology

Upstream source description

PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.

Quoted source text, attributed separately from HOL analysis.