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Fencer Vulns
medium 5.4

CVE-2026-48523 json

PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys

published 2026-05-28 5 mo ago modified 2026-10-25 14 d ago also EUVD-2026-32918 , GHSA-jq35-7prp-9v3f , PYSEC-2026-176

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

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 private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.

Patch / fix

  • pypi pyjwt 2.12.1, 2.13.0
  • pyjwt_project pyjwt 2.13.0
  • pyjwt Debian 14 2.13.0-1

debian advisories DEBIAN-CVE-2026-48523

  • pyjwt Ubuntu 26.04 LTS 2.10.1-4ubuntu1.1

ubuntu advisories UBUNTU-CVE-2026-48523

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-PyJWT SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +9 more 2.4.0-150200.3.14.1
  • python-PyJWT SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +9 more 2.8.0-150400.8.13.1
  • python-PyJWT SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 2.12.1-160000.2.1
  • python-PyJWT Linux Micro 6.1 2.12.1-slfo.1.1_2.1
  • python-PyJWT Linux Micro 6.0 2.9.0-3.1

suse advisories SUSE-SU-2026:2627-1SUSE-SU-2026:2626-1SUSE-SU-2026:22170-1SUSE-SU-2026:22220-1SUSE-SU-2026:22138-1SUSE-SU-2026:22238-1

  • python-PyJWT openSUSE Leap 16.0 2.12.1-160000.2.1
  • python-PyJWT openSUSE Tumbleweed 2.13.0-1.1

opensuse advisories openSUSE-SU-2026:21095-1openSUSE-SU-2026:11024-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-48523 updated cvss 5.4

python-pyjwt: PyJWT: Verifier-side algorithm bypass leads to unauthorized information access

  • Red Hat Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9, openshift-lightspeed/lightspeed-service-api-rhel9, openshift-lightspeed/lightspeed-to-dataverse-exporter-rhel9 Red Hat AI Inference Server rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9 Red Hat Ansible Automation Platform 2 python-pyjwt, automation-controller, ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-27/hub-rhel9, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-27/gateway-rhel9, +19 more Red Hat Enterprise Linux 9 fence-virt, fence-virtd, fence-agents, fence-virtd-cpg, fence-virtd-tcp, fence-agents-all, +51 more Red Hat Enterprise Linux 10 fence-agents-common
    +5 more products
    Red Hat OpenShift AI (RHOAI) rhoai/odh-vllm-gaudi-rhel9, rhoai/odh-kserve-agent-rhel9, rhoai/odh-kserve-router-rhel9, rhoai/odh-feature-server-rhel9, rhoai/odh-llama-stack-core-rhel9, rhoai/odh-kserve-controller-rhel9, +17 more Red Hat Quay 3 quay/quay-rhel8, quay/quay-rhel9 Red Hat Satellite 6 python-pyjwt, python3-pyjwt, satellite/foreman-mcp-server-rhel9, satellite/iop-host-inventory-rhel9 Red Hat Trusted Artifact Signer rhtas/segment-reporting-rhel9, rhtas/model-transparency-rhel9 Red Hat Update Infrastructure 4 for Cloud Providers python-pyjwt
    affected: workaround, no fix available “Fix deferred”
  • Red Hat AI Inference Server rhaii/vllm-cpu-rhel9, rhaii/vllm-tpu-rhel9, rhaii/vllm-cuda-rhel9, rhaii/vllm-rocm-rhel9, rhaii/vllm-gaudi-rhel9, rhaii/vllm-spyre-rhel9, +3 more Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9, +1 more Red Hat Hardened Images llvm, rust, llvm21 Red Hat OpenShift AI (RHOAI) rhoai/odh-llm-d-kv-cache-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
GitHub 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
OSV 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi pyjwt
>=2.9.0, <2.13.0
>=2.9.0, <2.12.1
2.13.0
2.12.1

Affected products

  • jpadilla pyjwt

Classification

Weakness
  • CWE-347 Improper Verification of Cryptographic Signature

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.