CVE-2026-48523: PyJWT is a JSON Web Token implementation in Python

Routine

MEDIUM 5.4UPGRADE

CVE-2026-48523 is a medium-severity flaw (CVSS 5.4) affecting pyjwt. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS pri

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.1% (top 98%)
CISA exploited list	No
Weakness	CWE-347
Published	2026-05-28
Last modified	2026-10-25

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

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-28 16:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

pyjwt project pyjwt UPGRADE

Affected: >= 2.9.0 and < 2.13.0

Fixed in: 2.13.0

Safe to downgrade to: a release before 2.9.0

1. Check installed version

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

2. UPGRADE to 2.13.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pyjwt

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pyjwt

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.9.0 (Debian / Ubuntu)

apt-cache madison pyjwt sudo apt install pyjwt=<VERSION_BEFORE_2.9.0> sudo apt-mark hold pyjwt

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list pyjwt sudo dnf downgrade pyjwt-<VERSION_BEFORE_2.9.0> 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.

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-2026-48523?

pyjwt: upgrade to 2.13.0. Exact commands for each OS are on this page.

Is CVE-2026-48523 being exploited?

CVE-2026-48523 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-2026-48523 affect?

CVE-2026-48523 affects pyjwt. Severity is medium (CVSS 5.4). PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against t

How urgent is CVE-2026-48523?

Priority 24/100. Public exploit reference

Software pages

Python vulnerabilities

Related CVEs

CVE-2026-48525 MEDIUM 5.3 UPGRADE PyJWT is a JSON Web Token implementation in Python

References

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