medium 5.3

CVE-2026-48525 json

PyJWT: Unauthenticated DoS via unbounded Base64URL decoding of unused payload segment in b64=false detached JWS

published 2026-05-28 5 mo ago modified 2026-10-25 14 d ago also EUVD-2026-32919 , GHSA-w7vc-732c-9m39 , PYSEC-2026-178

cvss: 5.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 31%
public exploits: 0; none known

PyJWT is a JSON Web Token implementation in Python. From 2.8.0 to 2.12.1, when verifying detached JWS tokens using the unencoded-payload option ("b64": false, RFC 7797), PyJWT performs Base64URL decoding of the compact-serialization payload segment before enforcing the detached-payload rules. For b64=false, PyJWT later discards that decoded payload and replaces it with the caller-provided detached_payload. In practice, this turns the middle segment into an attacker-controlled “work amplifier”: a remote client can supply an arbitrarily large Base64URL payload segment that forces CPU work + memory allocations even if the signature is invalid. This creates an unauthenticated DoS vector against any endpoint that verifies detached JWS using PyJWT. This vulnerability is fixed in 2.13.0.

Patch / fix

fixed in 2 distros 5

pypi pyjwt 2.13.0
pyjwt_project pyjwt 2.13.0

debian ubuntu suse opensuse azure linux

pyjwt Debian 14 2.13.0-1

debian advisories DEBIAN-CVE-2026-48525

pyjwt Ubuntu 24.04 LTS 2.7.0-1ubuntu0.2
pyjwt Ubuntu 26.04 LTS 2.10.1-4ubuntu1.1

ubuntu advisories UBUNTU-CVE-2026-48525

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-2026:2627-1 SUSE-SU-2026:2626-1 SUSE-SU-2026:22170-1 SUSE-SU-2026:22220-1 SUSE-SU-2026:22138-1 SUSE-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-2026:21095-1 openSUSE-SU-2026:11024-1

python-jwt Azure Linux 3.0 2.13.0-1

azure linux advisories AZL-93042

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-48525 updated 2026-11-05 cvss 5.3

python-pyjwt: PyJWT: Denial of Service via processing of crafted detached JWS tokens

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 rhaii/vllm-cpu-rhel9, rhaii/vllm-tpu-rhel9, rhaii/vllm-cuda-rhel9, rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9, rhaii/vllm-gaudi-rhel9, +2 more 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

+6 more productsfewer

Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9 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-llm-d-kv-cache-rhel9, rhoai/odh-llama-stack-core-rhel9, +18 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-rocm-rhel9, rhaiis/vllm-cuda-rhel9, rhaiis/vllm-rocm-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-rocm-rhel9, rhelai3/bootc-azure-rocm-rhel9
not affected: vulnerable code not present
Red Hat Hardened Images llvm, rust, llvm21
not affected: vulnerable code not in execute path

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: yes
Technical impact: partial
Assessed: 5 mo ago (2026-05-28)

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 31% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
OSV	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem	package	affected	fixed in
pypi	pyjwt	>=2.8.0, <2.13.0	2.13.0

Affected products

jpadilla pyjwt

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption

References

github.com /jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39
exploit, web, mitigation, vendor-advisory, evidence
nvd.nist.gov /vuln/detail/CVE-2026-48525
advisory
github.com /jpadilla/pyjwt
package
github.com /pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-178.yaml
web

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.

Summary