CVE-2025-66471 json
urllib3 Streaming API improperly handles highly compressed data
published 2025-12-05 11 mo ago modified 2026-09-25 44 d ago also EUVD-2025-201419 , GHSA-2xpw-w6gg-jr37 , PYSEC-2026-1994
- cvss
- 7.5
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.7%
- EPSS 0.7% chance of exploitation in 30 days, percentile 54%
- public exploits
- 0
- none known
Summary
urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.0 and prior to 2.6.0, the Streaming API improperly handles highly compressed data. urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation. The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data.
Patch / fix
- pypi urllib3 2.6.0
- python urllib3 2.6.0
- python-urllib3 Debian 14 2.6.3-1
debian advisories DEBIAN-CVE-2025-66471
- python-urllib3 Ubuntu 24.04 LTS 2.0.7-1ubuntu0.3
- python-urllib3 Ubuntu 25.10 2.3.0-3ubuntu0.1
- python-urllib3 Ubuntu 26.04 LTS 2.5.0-1ubuntu1
- python-pip Ubuntu Pro 22.04 LTS 22.0.2+dfsg-1ubuntu0.7+esm3
- python-pip Ubuntu Pro 24.04 LTS 24.0+dfsg-1ubuntu1.3+esm3
- python-pip Ubuntu Pro 26.04 LTS 25.1.1+dfsg-1ubuntu2+esm3
ubuntu advisories UBUNTU-CVE-2025-66471
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-urllib3 openstack 17.1 1.26.5-3.el8ost.3
- python3-urllib3 openstack 17.1 1.26.5-3.el8ost.3
- receptor ansible automation platform 2.6 1.6.3-2.el10ap
- receptor ansible automation platform inside 2.6, ansible automation platform developer 2.6, ansible automation platform 2.6 1.6.3-2.el9ap
- python3.11-django ansible automation platform developer 2.6, ansible automation platform 2.6 4.2.27-2.el9ap
- python3.11-urllib3 ansible automation platform developer 2.6, ansible automation platform 2.6 2.6.3-1.el9ap
- python3.11-protobuf ansible automation platform 2.6 4.25.8-1.el9ap
- automation-controller-venv-tower ansible automation platform 2.6 4.7.8-1.el9ap
red hat advisories RHSA-2026:28043RHSA-2026:11722RHSA-2026:9031RHSA-2026:1249RHSA-2026:2765RHSA-2026:2764
- python-urllib3 SLE Module for Python 3 15 SP7, SLE Module for Public Cloud 15 SP4, SLE High Performance Computing 15 SP5-ESPOS +10 more 2.0.7-150400.7.27.1
- python-urllib3 SLE Module for Basesystem 15 SP7, SLE Micro 5.5, SLE Micro 5.4 +11 more 1.25.10-150300.4.30.1
- python-urllib3 SLES LTSS Extended Security 12 SP5, SLE Module for Public Cloud 12 1.25.10-3.48.4
- python-urllib3 SLE Module for Basesystem 15 SP7, SLE Micro 5.5, SLE Micro 5.4 +2 more 1.25.10-150300.4.24.1
- python-urllib3_1 SLES for SAP applications 16.0, SLES 16.0 1.26.20-160000.3.1
- python-urllib3_1 SLE Module for Python 3 15 SP7, openSUSE Leap 15.6 1.26.18-150600.3.6.1
- python-urllib3 Linux Micro 6.1 2.1.0-slfo.1.1_4.1
- python-urllib3 Linux Micro 6.0 2.1.0-5.1
suse advisories SUSE-SU-2026:0367-2SUSE-SU-2026:2854-2SUSE-SU-2026:2854-1SUSE-SU-2026:1412-1SUSE-SU-2026:1067-1SUSE-SU-2026:20591-1
- python-urllib3_1 openSUSE Leap 16.0 1.26.20-160000.3.1
- python-urllib3 openSUSE Leap 16.0 2.5.0-160000.4.1
- python-urllib3_1 openSUSE Tumbleweed 1.26.20-5.1
- python-urllib3 openSUSE Tumbleweed 2.6.2-1.1
opensuse advisories openSUSE-SU-2026:20271-1openSUSE-SU-2026:20127-1openSUSE-SU-2026:10096-1openSUSE-SU-2026:10026-1
- python3-urllib3 AlmaLinux 10 1.26.19-2.el10_1.1
- python3-urllib3 AlmaLinux 9 1.26.5-6.el9_7.1
- python3.12-urllib3 AlmaLinux 9 1.26.19-1.el9_7.1
- python3.11-urllib3 AlmaLinux 9 1.26.12-5.el9_7.1
- python3.11-urllib3 AlmaLinux 8 1.26.12-6.el8_10
- python3.12-urllib3 AlmaLinux 8 1.26.19-2.el8_10
- fence-virt AlmaLinux 9 4.10.0-98.el9_7.4
- fence-virtd AlmaLinux 9 4.10.0-98.el9_7.4
almalinux advisories ALSA-2026:1086ALSA-2026:1087ALSA-2026:1088ALSA-2026:1089ALSA-2026:1224ALSA-2026:1226
- fence-agents Rocky Linux 8 4.2.1-129.el8_10.20
- python-urllib3 Rocky Linux 10 1.26.19-2.el10_1.1
- python-urllib3 Rocky Linux 9 1.26.5-6.el9_7.1
- python3.12-urllib3 Rocky Linux 9 1.26.19-1.el9_7.1
- python3.11-urllib3 Rocky Linux 9 1.26.12-5.el9_7.1
- fence-agents Rocky Linux 9 4.10.0-98.el9_7.4
- resource-agents Rocky Linux 8 4.9.0-54.el8_10.27
- python3.11-urllib3 Rocky Linux 8 1.26.12-6.el8_10
rocky linux advisories RLSA-2026:1240RLSA-2026:1086RLSA-2026:1087RLSA-2026:1088RLSA-2026:1089RLSA-2026:1239
- py3-urllib3 Alpine 3.23 2.6.3-r0
alpine advisories ALPINE-CVE-2025-66471
Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0
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-2025-66471 updated cvss 7.5
urllib3: urllib3 Streaming API improperly handles highly compressed data
-
Red Hat Builds for Red Hat OpenShift openshift-builds/openshift-builds-shared-resource-webhook-rhel9affected: workaround, no fix available
-
Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/logging-curator5-rhel9affected: workaround, no fix planned “Will not fix”
-
Red Hat Migration Toolkit for Containers rhmtc/openshift-migration-rhel8-operator, rhmtc/openshift-migration-hook-runner-rhel8affected: workaround, no fix available, no fix planned “Will not fix”
-
Red Hat Migration Toolkit for Virtualization mtv-candidate/mtv-rhel9-operator, mtv-candidate/mtv-virt-v2v-rhel9, mtv-candidate/mtv-must-gather-rhel8, mtv-candidate/mtv-cli-download-rhel9, mtv-candidate/mtv-console-plugin-rhel9, migration-toolkit-virtualization/mtv-virt-v2v-rhel9affected: workaround, no fix planned “Will not fix”
-
Red Hat Multiarch Tuning Operator multiarch-tuning/multiarch-tuning-rhel9-operatoraffected: workaround, no fix available
-
Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-service-api-rhel9, openshift-lightspeed-tech-preview/lightspeed-rag-tool-rhel9, openshift-lightspeed/lightspeed-to-dataverse-exporter-rhel9 Red Hat OpenShift Pipelines openshift-pipelines/pipelines-events-rhel8, openshift-pipelines/pipelines-hub-ui-rhel8, openshift-pipelines/pipelines-hub-ui-rhel9, openshift-pipelines/pipelines-cli-tkn-rhel8, openshift-pipelines/pipelines-hub-api-rhel8, openshift-pipelines/pipelines-webhook-rhel8, +27 moreaffected: workaround, no fix available, no fix planned “Will not fix”
-
Red Hat OpenShift Serverless openshift-serverless-1/kn-eventing-integrations-transform-jsonata-rhel9affected: workaround, no fix planned “Will not fix”
-
Red Hat AI Inference Server rhaiis/vllm-tpu-rhel9, rhaiis/vllm-spyre-rhel9, rhai/base-image-cpu-rhel9, rhai/base-image-cuda-rhel9, rhai/base-image-rocm-rhel9, rhaiis-preview/vllm-cuda-rhel9affected: workaround, no fix available
show 21 moreshow fewer
-
Red Hat Ansible Automation Platform 2 ansible-automation-platform-25/gateway-rhel8, ansible-automation-platform-26/hub-web-rhel9, ansible-automation-platform-24/de-minimal-rhel8, ansible-automation-platform-24/de-minimal-rhel9, ansible-automation-platform-25/de-minimal-rhel8, ansible-automation-platform-25/ee-minimal-rhel8, +17 more Red Hat Ansible Automation Platform Ansible Core 2 ansible-automation-platform/ee-minimal-rhel8, ansible-automation-platform/ee-minimal-rhel9, ansible-automation-platform-tech-preview/ee-minimal-rhel8, ansible-automation-platform-tech-preview/ee-minimal-rhel9affected: workaround, no fix available, no fix planned “Will not fix”
-
Red Hat Ceph Storage 6 python3.11-urllib3 Red Hat Ceph Storage 7 python3.11-urllib3 Red Hat Ceph Storage 8 rhceph/grafana-rhel9 Red Hat Ceph Storage 9 python3.11-urllib3 Red Hat Certification Program for Red Hat Enterprise Linux 9 rhcertification/redhat-certification-baremetal, rhcertification/redhat-certification-system-aiaffected: workaround, no fix available
-
Red Hat Connectivity Link 1 rhcl-1/limitador-rhel9, rhcl-1/wasm-shim-rhel9, rhcl-1/rhcl-console-plugin-rhel9affected: workaround, no fix available, no fix planned “Will not fix”
-
Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9affected: workaround, no fix available “Fix deferred”
-
Red Hat Discovery 2 discovery/discovery-server-rhel9 Red Hat Edge Manager preview rhem/flightctl-db-setup-rhel9, rhem/flightctl-cli-artifacts-rhel9affected: workaround, no fix available
-
Red Hat Enterprise Linux 9 rhel9/bootc-image-builder, rhel9-eus/rhel-9.6-bootc-image-builder Red Hat Enterprise Linux 10 rhel10/bootc-image-builder, rhel10-eus/rhel-10.0-bootc-image-builder 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/disk-image-cuda-rhel9, +1 more Red Hat OpenShift AI (RHOAI) rhoai/odh-caikit-nlp-rhel9, rhoai/odh-llama-stack-core-rhel9, rhoai/odh-modelmesh-runtime-adapter-rhel8, rhoai/odh-ml-pipelines-runtime-generic-rhel9, rhoai/odh-trustyai-ragas-lls-provider-dsp-rhel9 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9, openshift4/oc-mirror-plugin-rhel9, openshift4/ose-olm-catalogd-rhel8, openshift4/ose-olm-catalogd-rhel9, openshift4/ose-operator-registry-rhel9, openshift4/ose-cluster-olm-rhel9-operator, +4 moreaffected: workaround, no fix available, no fix planned “Will not fix”
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Red Hat Openshift Data Foundation 4 odf4/mcg-core-rhel9, odf4/ocs-client-console-rhel9affected: workaround, no fix available
-
Red Hat OpenShift Dev Spaces devspaces/jetbrains-ide-rhel9, devspaces-tech-preview/jetbrains-ide-rhel9affected: workaround, no fix planned “Will not fix”
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Red Hat Satellite 6 python-urllib3, python3-urllib3, satellite/iop-vmaas-rhel9, satellite/iop-yuptoo-rhel9, satellite/iop-host-inventory-rhel9, satellite/iop-advisor-backend-rhel9affected: workaround, no fix available
-
Red Hat Builds for Red Hat OpenShift 1.6.0 openshift-builds 1773931994fixed: vendor fix RHSA-2026:5549
-
Red Hat Cert Manager support for Red Hat OpenShift release 1.18 cert-manager 1768985261, cert-manager 1768985286, cert-manager 1769093352, cert-manager 1769093403, cert-manager 1769093421, cert-manager 1769419247, +2 morefixed: vendor fix RHSA-2026:1038
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Red Hat mirror registry for Red Hat OpenShift 2.0 openshift/mirror-registry-rhel8 1782177012fixed: vendor fix RHSA-2026:28441
-
Red Hat Multicluster Global Hub 1.4.9 multicluster-globalhub 1770126537fixed: vendor fix RHSA-2026:2500
-
Red Hat Multicluster Global Hub 1.5.8 multicluster-globalhub 1770109405fixed: vendor fix RHSA-2026:2256
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Red Hat Network Observability (NETOBSERV) 1.11.0 network-observability 1771226060fixed: vendor fix RHSA-2026:2900
-
Red Hat OpenShift API for Data Protection 1.3 oadp 1770420495, oadp 1770420562, oadp 1770420563, oadp 1770420565, oadp 1770420728, oadp 1770420975, +4 morefixed: vendor fix RHSA-2026:3444
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Red Hat Advanced Cluster Security 4.8 advanced-cluster-security 1771402244, advanced-cluster-security 1772474383, advanced-cluster-security 1773235880fixed: vendor fix RHSA-2026:4466
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Red Hat Advanced Cluster Security 4.9 advanced-cluster-security 1771401314, advanced-cluster-security 1773235860fixed: vendor fix RHSA-2026:4467
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Red Hat AI Inference Server 3.2 rhaiis 1772160593, rhaiis 1772160625, rhaiis/model-opt-cuda-rhel9 1787772157fixed: vendor fix RHSA-2026:61628
-
Red Hat Ansible Automation Platform 2.4 ansible-automation-platform-24 1768268588fixed: vendor fix RHSA-2026:1599
-
Red Hat Ansible Automation Platform 2.4 for RHEL 8 automation-controller-venv-tower 4.5.30-1.el8apfixed: vendor fix RHSA-2026:1497
86 more fixed, 80 more not affected in the full advisory
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
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 11 mo ago
Exploit prediction
0.73% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.9 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H |
| CNA | 4.0 | 8.9 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | urllib3 | >=1.0, <2.6.0 |
2.6.0 |
Affected products
- urllib3 urllib3
Classification
- Weakness
-
- CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)
References
-
github.com
/urllib3/urllib3/commit/c19571de34c47de3a766541b041637ba5f716ed7
web, patch
-
github.com
/urllib3/urllib3/commit/d0fde3672e4a4093f7587858dccfc298eb66e46c
web
-
github.com
/urllib3/urllib3/security/advisories/GHSA-2xpw-w6gg-jr37
web, vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2025-66471
advisory
-
github.com
/advisories/GHSA-2xpw-w6gg-jr37
advisory
-
github.com
/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2026-1994.yaml
web
-
github.com
/urllib3/urllib3
package
-
pypi.org
/project/urllib3
web, package
Sources
- CVE List CVE-2025-66471
- GitHub Advisory GHSA-2xpw-w6gg-jr37
- NVD CVE-2025-66471
- OSV PYSEC-2026-1994
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.