CVE-2026-102266: PyJWT is a Python implementation of JSON Web Token standards

This week

HIGH 7.4REMOTEDOWNGRADE

CVE-2026-102266 is a high-severity flaw (CVSS 7.4) affecting pyjwt. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 authenticate

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-347
Published	2026-09-28
Last modified	2026-10-07

Publisher (CNA): GitHub, Inc. · Vendor: pyjwt project

Last updated 2026-10-07 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-28 21:17 UTCPublished CVE record published
2026-10-07 20:55 UTCUpdated Record last modified

pyjwt project pyjwt DOWNGRADE

Affected: 2.13.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.13.0

1. Check installed version

apt-cache policy pyjwt || rpm -q pyjwt || pyjwt --version

2. No fixed release: DOWNGRADE to a release before 2.13.0 (Debian / Ubuntu)

apt-cache madison pyjwt sudo apt install pyjwt=<VERSION_BEFORE_2.13.0> sudo apt-mark hold pyjwt

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list pyjwt sudo dnf downgrade pyjwt-<VERSION_BEFORE_2.13.0> sudo dnf versionlock add pyjwt

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Advisories and coverage

Official advisories

Amazon Linux 2023 ALAS: ALAS2023-2026-3298 (important): python-jwt 2026-10-24

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-102266?

pyjwt: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-102266 being exploited?

CVE-2026-102266 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-102266 affect?

CVE-2026-102266 affects pyjwt. Severity is high (CVSS 7.4). 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 trus

How urgent is CVE-2026-102266?

Priority 39/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

Related CVEs

CVE-2026-48526 HIGH 7.4 UPGRADE PyJWT is a JSON Web Token implementation in Python
CVE-2026-48524 LOW 3.7 UPGRADE PyJWT is a JSON Web Token implementation in Python
CVE-2026-48522 MEDIUM 4.2 UPGRADE PyJWT is a JSON Web Token implementation in Python
CVE-2026-48525 MEDIUM 5.3 UPGRADE PyJWT is a JSON Web Token implementation in Python
CVE-2026-48523 MEDIUM 5.4 UPGRADE PyJWT is a JSON Web Token implementation in Python

References

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