CVE-2025-66418: urllib3 allows an unbounded number of links in the decompression chain

Analyzed

AliasesALPINE-CVE-2025-66418GHSA-gm62-xv2j-4w53PYSEC-2026-1998+337 more

Published 05-12-2025Last modified 05-12-2025

Vulnerability summary

CVE-2025-66418 is a high (CVSS 8.9) vulnerability in python urllib3. EPSS estimates a 0.68% chance of exploitation in the next 30 days, higher than 52.5% of scored vulnerabilities.

Priority

Prioritisesevere

Severe, CVSS 8.9 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?

CVSS score

8.9/10

010

High · v4.0 (CVE.org)

EPSS score

0.68%

0%100%

Low · 0.00 pp in 30 days

KEVNot listedNot listed by any tracked catalog.

RansomwareNot flaggedNo ransomware use recorded.

Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 48 · Related 23

DLA-4421-1 DSA-6102-1 MGASA-2026-0011 OPENSUSE-SU-2026:10026-1 OPENSUSE-SU-2026:10096-1 OPENSUSE-SU-2026:10539-1+49 more

Timeline

05-12-2025
PublishedVulnerability first disclosed.
05-12-2025
Last modifiedVulnerability information updated.

Description

urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.24 and prior to 2.6.0, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data. This vulnerability is fixed in 2.6.0.

CVSS metrics

11 scores · 9 sources · 2 versions

v4.08.9v3.17.5

EPSS trend

Probability

0.68%

Chance of exploitation in the next 30 days

Percentile

53%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.68% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs

CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard158 products

airflow-2< 2.11.0-r16
airflow-2-bitnami-compat< 2.11.0-r16
airflow-2-compat< 2.11.0-r16
airflow-2-iamguarded-compat< 2.11.0-r16
airflow-3< 3.1.4-r0

airflow-3-bitnami-compat< 3.1.4-r0
airflow-3-compat< 3.1.4-r0
airflow-3-iamguarded-compat< 3.1.4-r0
airflow-core-2< 2.11.0-r9
airflow-core-2-compat< 2.11.0-r9
airflow-core-2-oci-entrypoint< 2.11.0-r9
airflow-core-3< 3.1.3-r1
airflow-core-3-compat< 3.1.3-r1
airflow-core-3-oci-entrypoint< 3.1.3-r1
ansible-operator< 1.42.2-r2 | < 1.42.0-r6
ansible-operator-fips< 1.42.0-r1 | < 1.42.2-r2
apache-beam-python-3.11-sdk< 2.69.0-r2
authentik< 2025.10.2-r3
authentik-go-server< 2025.10.2-r3
awx< 24.6.1-r33 | < 24.6.1-r20
az< 2.81.0-r1
azure-functions-host-python3.11-worker< 4.1048.200-r1
azure-functions-host-python3.12-worker< 4.1048.200-r1
azure-functions-host-python3.13-worker< 4.1048.200-r1
barman< 3.16.2-r1
barman-cloudnative-pg< 3.16.2-r1
confluent-docker-utils< 0.0.162-r4
dask-gateway< 2025.4.0-r7
dask-gateway-server< 2025.4.0-r7
dask-kubernetes< 2025.7.0-r2
datadog-agent-7.71< 7.71.2-r22
datadog-agent-7.71-core-integrations< 7.71.2-r22 | All versions (No fix recorded)
datadog-agent-7.72< 7.72.4-r22
datadog-agent-7.72-core-integrations< 7.72.4-r22
datadog-agent-7.73< 7.73.3-r13
datadog-agent-7.73-core-integrations< 7.73.3-r13
datadog-agent-7.74< 7.74.1-r15
datadog-agent-7.74-core-integrations< 7.74.1-r15
datadog-agent-7.75< 7.75.4-r7
datadog-agent-7.75-core-integrations< 7.75.4-r7
datadog-agent-7.76< 7.76.3-r41 | All versions (No fix recorded) | < 7.76.3-r15
datadog-agent-7.76-core-integrations< 7.76.3-r15
datadog-agent-7.77< 7.77.3-r6
datadog-agent-7.77-core-integrations< 7.77.3-r6
datadog-agent-fips-7.71< 7.71.2-r15
datadog-agent-fips-7.71-core-integrationsAll versions (No fix recorded) | < 7.71.2-r15
datadog-agent-fips-7.72< 7.72.4-r15 | < 7.72.4-r14
datadog-agent-fips-7.72-core-integrations< 7.72.4-r14 | < 7.72.4-r15
datadog-agent-fips-7.73< 7.73.3-r12
datadog-agent-fips-7.73-core-integrations< 7.73.3-r12
datadog-agent-fips-7.74< 7.74.1-r12
datadog-agent-fips-7.74-core-integrations< 7.74.1-r12
datadog-agent-fips-7.75< 7.75.4-r5
datadog-agent-fips-7.75-core-integrations< 7.75.4-r5
datadog-agent-fips-7.76< 7.76.3-r12
datadog-agent-fips-7.76-core-integrations< 7.76.3-r12
datadog-agent-fips-7.77< 7.77.3-r7
datadog-agent-fips-7.77-core-integrations< 7.77.3-r7 | < 7.77.3-r6
emissary< 3.10.0-r14
emissary-apiext< 3.10.0-r14
emissary-oci-entrypoint< 3.10.0-r14
ggshield< 1.48.0-r0
gitlab-toolbox-ce-18.6All versions (No fix recorded)
gitlab-toolbox-ce-18.7All versions (No fix recorded)
gitlab-toolbox-ce-18.8All versions (No fix recorded)
gitlab-toolbox-ce-fips-18.6All versions (No fix recorded)
gitlab-toolbox-ce-fips-18.7All versions (No fix recorded)
gitlab-toolbox-ce-fips-18.8All versions (No fix recorded)
graalvm-24-graalpy-venvAll versions (No fix recorded)
graalvm-25-graalpy-venv< 25.0.2-r10
jupyter-base-notebook< 7.5.0-r1
jupyter-docker-base< 999.9.9_git20260925-r0
jupyter-docker-stacks< 999.9.9_git20260925-r0 | < 7.3.2-r1
jwt-tool< 2.3.0-r3
k8s-sidecar< 2.1.4-r1
katib-earlystopping< 0.19.0-r15 | < 0.19.0-r3
katib-suggestion-hyperband< 0.19.0-r14 | < 0.19.0-r13
katib-suggestion-hyperopt< 0.19.0-r14 | < 0.19.0-r13
katib-suggestion-nas-darts< 0.19.0-r13 | < 0.19.0-r14
katib-suggestion-optuna-enas< 0.19.0-r14 | < 0.19.0-r13
katib-suggestion-pbt-enas< 0.19.0-r13
katib-suggestion-skopt-enas< 0.19.0-r13
kserve< 0.16.0-r6
kserve-agent< 0.16.0-r6
kserve-agent-compat< 0.16.0-r6
kserve-manager< 0.16.0-r6
kserve-manager-compat< 0.16.0-r6
kserve-qpext< 0.16.0-r6
kserve-qpext-compat< 0.16.0-r6
kserve-router< 0.16.0-r6
kserve-router-compat< 0.16.0-r6
kserve-storage-controller< 0.16.0-r6 | < 0.16.0-r3
kubeflow-jupyter-web-app< 1.10.0-r8
kubeflow-pipelines< 2.15.0-r4
kubeflow-pipelines-cache_server< 2.15.0-r4
kubeflow-pipelines-frontend< 2.15.0-r4
kubeflow-pipelines-metadata-envoy-config< 2.15.0-r4
kubeflow-pipelines-metadata-writer< 2.15.0-r4
kubeflow-pipelines-metadata-writer-compat< 2.15.0-r4
kubeflow-pipelines-persistence_agent< 2.15.0-r4
kubeflow-pipelines-scheduledworkflow< 2.15.0-r4
kubeflow-pipelines-viewer-crd-controller< 2.15.0-r4
kubeflow-pipelines-visualization-server< 2.15.0-r0
kubeflow-volumes-web-app< 1.10.0-r6
localstack< 4.12.0-r0 | < 4.14.0-r6
mlflow< 3.7.0-r1
mlflow-iamguarded-compat< 3.7.0-r1
nemo< 2.6.0-r0 | < 2.7.3-r2 | < 2.6.1-r1
nvidia-nsight-compute-13.1< 2025.4.1.2-r1 | < 2025.4.0.12-r0
nvidia-nsight-compute-13.2< 2026.1.1.2-r2
nvidia-nsight-compute-13.3< 2026.2.1.5-r1
open-webui< 0.8.12-r4 | < 0.9.2-r0
openstack-kolla-toolbox-2025.1< 20.4.0-r3
openstack-kolla-toolbox-2025.1-fips< 20.4.0-r2
openstack-kolla-toolbox-2025.2< 21.1.0-r2
openstack-kolla-toolbox-2025.2-fips< 21.1.0-r2
pgadmin4< 9.12-r1 | < 9.11-r0
pgadmin4-fips< 9.12-r1
py3-cassandra-medusa< 0.27.0-r1 | < 0.28.0-r1
py3-hashin< 1.0.5-r5
py3-semgrep< 1.145.0-r0
py3-supported-urllib3< 2.6.1-r0
py3-urllib3< 2.6.1-r0
py3.10-ambassador< 3.10.0-r14
py3.10-pip-base< 26.1.1-r0
py3.10-pipenv< 2026.6.0-r0
py3.10-urllib3< 2.6.1-r0
py3.11-ambassador< 3.10.0-r14
py3.11-pip-base< 26.1.1-r0
py3.11-pipenv< 2026.6.0-r0
py3.11-text-generation-inference< 3.3.7-r2
py3.11-urllib3< 2.6.1-r0
py3.12-ambassador< 3.10.0-r14
py3.12-pip-base< 26.1.1-r0
py3.12-pipenv< 2026.6.0-r0
py3.12-urllib3< 2.6.1-r0
py3.13-ambassador< 3.10.0-r14
py3.13-pip-base< 26.1.1-r0
py3.13-pipenv< 2026.6.0-r0
py3.13-scanner-test-libraries< 0.0.1-r2
py3.13-scanner-test-scanner-test-python-vulnerability-fixedAll versions (No fix recorded)
py3.13-scanner-test-scanner-test-python-vulnerability-unfixedAll versions (No fix recorded)
py3.13-urllib3< 2.6.1-r0
py3.14-pip-base< 26.1.1-r0
py3.9-pipAll versions (No fix recorded)
pypy-3.10< 7.3.19-r16
pypy-3.11< 7.3.22-r0
request-1276< 0.27.1-r1 | < 0.26.0-r2
semgrep< 1.145.0-r0
spamcheck< 3.5.3-r4
spamcheck-compat< 3.5.3-r4
superset-5.0< 5.0.0-r9
superset-5.0-entrypoint< 5.0.0-r9
superset-5.0-iamguarded-compat< 5.0.0-r9
tensorflow-cpu-jupyter< 2.20.0-r6 | < 2.21.0-r2
tensorflow-gpu-jupyter< 2.20.0-r5 | < 2.21.0-r2
tritonserver-backend-vllm-cuda-12.9< 25.9.0_git20251112-r2
tritonserver-backend-vllm-meta-cuda-12.9< 25.9.0_git20251112-r2

Show all 158

Wolfi41 products

airflow-3< 3.1.4-r0
airflow-3-bitnami-compat< 3.1.4-r0
airflow-3-compat< 3.1.4-r0
airflow-3-iamguarded-compat< 3.1.4-r0
az< 2.81.0-r1

Show all 41

Alpine1 product

py3-urllib3< 2.6.3-r0

3 vendors · 200 products · Showing 200 of 336

References

43 links

github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53X Refsource CONFIRMWEBARTICLEREPORTAdvisoryVendor Advisory
github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8X Refsource MISCWEBFIXARTICLEPatch
security.alpinelinux.org/vuln/CVE-2025-66418Advisory
nvd.nist.gov/vuln/detail/CVE-2025-66418AdvisoryOval
github.com/urllib3/urllib3PACKAGE
pypi.org/project/urllib3PACKAGE
github.com/advisories/GHSA-gm62-xv2j-4w53Advisory
access.redhat.com/errata/RHSA-2026:1329Advisory
access.redhat.com/security/updates/classification/ARTICLE
bugzilla.redhat.com/show_bug.cgi?id=2419455REPORT

Show all 43 references