Reference page — cumulative record through Thursday, October 8, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-102266

CVE-2026-102266CRITICAL

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

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  H  H  N    9.1   .0018    6.3     —

AFFECTED
  Product  Versions               Fixed
  pyjwt    >= 2.13.0, < 2.14.0 –  —

TIMELINE
  Sep 28  Reserved by GitHub_M
  Sep 28  Published (CNA: GitHub_M)
  Oct 7   EXPLOIT PUBLISHED — CVE-2026-102266 (jpadilla pyjwt). Public exploit reference added.
  Oct 7   RESCORED — CVE-2026-102266 (jpadilla pyjwt). CVSS 7.4 → 9.1 (NVD).

CWE-347 · CNA: GitHub_M · CVSS v3.1 · 3 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
September 28, 2026	Reserved	Reserved by GitHub_M
September 28, 2026	Published	Published (CNA: GitHub_M)
October 7, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-102266 (jpadilla pyjwt). Public exploit reference added.
October 7, 2026	RESCORED	RESCORED — CVE-2026-102266 (jpadilla pyjwt). CVSS 7.4 → 9.1 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
jpadilla	pyjwt	—	>= 2.13.0, < 2.14.0	—

Weaknesses

CWE-347

References (3)

https://github.com/jpadilla/pyjwt/commit/f91ed44dd65baaf457f4b3353ed35e98a753934c [Patch]
https://github.com/jpadilla/pyjwt/releases/tag/2.14.0 [Product, Release Notes]
https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3r [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-102266 at cve.org

Vendors: jpadilla

Weaknesses: CWE-347

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-102266 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Thursday, October 8, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.