> CVE-2026-21441 [HIGH]

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PUBLISHED
2026-01-07 22:15
MODIFIED
2026-01-07 22:15
CVSS_SCORE V3
8.9
EPSS (Prob. Exploit)
2.92%
Top 12.9%
DATA SOURCES:
NVD 🔗 2026-01-07 RED HAT 🔗 2026-01-11 CVE PROJECT 🔗 2026-01-19 CWE MITRE 🔗 2026-11-01 FIRST EPSS 🔗 2026-11-08 GITHUB 🔗 2026-10-28 OSV 🔗 2026-11-08 MSRC 🔗 2026-11-02

> DESCRIPTION

urllib3 is an HTTP client library for Python. 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. urllib3 can perform decoding or decompression based on the HTTP `Content-Encoding` header (e.g., `gzip`, `deflate`, `br`, or `zstd`). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption. Starting in version 1.22 and prior to version 2.6.3, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client. Applications and libraries are affected when they stream content from untrusted sources by setting `preload_content=False` when they do not disable redirects. Users should upgrade to at least urllib3 v2.6.3, in which the library does not decode content of redirect responses when `preload_content=False`. If upgrading is not immediately possible, disable redirects by setting `redirect=False` for requests to untrusted source.

> AFFECTED_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> CVSS V3 METRICS

CVSS_VECTOR
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

> MÉTRIQUES CVSS DÉTAILLÉES

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
Métrique Valeur Interprétation
AV (Vecteur d'Attaque)
Attack Vector
Network (N)
Exploit possible à distance via réseau (HTTP, API, etc.)
AC (Complexité d'Attaque)
Attack Complexity
Low (L)
Peu de conditions requises pour exploiter
PR (Privilèges Requis)
Privileges Required
None (N)
Aucune authentification requise
UI (Interaction Utilisateur)
User Interaction
None (N)
Aucune interaction utilisateur nécessaire
S (Périmètre)
Scope
Unchanged (U)
Impact reste dans le périmètre du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
None (N)
Aucune divulgation d'informations
I (Impact Intégrité)
Integrity Impact
None (N)
Aucune modification de données possible
A (Impact Disponibilité)
Availability Impact
High (H)
Interruption totale du service possible

> RÉSUMÉ DES IMPACTS

Confidentialité
None
Aucune divulgation d'informations
Intégrité
None
Aucune modification de données possible
Disponibilité
High
Interruption totale du service possible

> WEAKNESSES

CWE-409

> CWE DETAILED DESCRIPTIONS

CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) - The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.

> RED HAT SECURITY ADVISORIES

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An update for python-urllib3 is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions, and Red Hat Ent...
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Red Hat Security Advisory: Satellite 6.16.6.1 Async Update
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Red Hat Security Advisory: Satellite 6.17.6.3 Async Update
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Red Hat Security Advisory: RHTAS 1.2.2 - Red Hat Trusted Artifact Signer Release
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Red Hat Security Advisory: RHTAS 1.2.2 - Red Hat Trusted Artifact Signer Release
The 1.2.2 release of Red Hat Trusted Artifact Signer OpenShift Operator. For more details please visit the product documentation at https://access.redhat.com/documentation/en-us/red_hat_trusted_artifa...
Red Hat Security Advisory: RHTAS 1.2.2 - Red Hat Trusted Artifact Signer Release
The 1.2.2 release of Red Hat Trusted Artifact Signer OpenShift Operator. For more details please visit the product documentation at https://access.redhat.com/documentation/en-us/red_hat_trusted_artifa...
Red Hat Security Advisory: RHTAS 1.2.2 - Red Hat Trusted Artifact Signer Release
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The Tech Preview release of the RHTAS Policy Controller Operator. For more details please visit the product documentation at https://access.redhat.com/documentation/en-us/red_hat_trusted_artifact_sign...
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A new version of OpenShift API for Data Protection (OADP) is now available.
Red Hat Security Advisory: New container image: rhceph-9.0
A new version of Red Hat build of Ceph Storage has been released
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Red Hat AI Inference Server 3.2.2 (ROCm) is now available.
Red Hat Security Advisory: Red Hat AI Inference Server 3.2.2 (CUDA)
Red Hat AI Inference Server 3.2.2 (CUDA) is now available.
Red Hat Security Advisory: RHOAI 2.25.3 - Red Hat OpenShift AI
Updated images are now available for Red Hat OpenShift AI.
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Red Hat Security Advisory: RHTAS 1.3.2 - Tech Preview Release of Model Transparency
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Red Hat Security Advisory: General availability of the satellite/iop-advisor-frontend-rhel9 container image
A new satellite/iop-advisor-frontend-rhel9 container image is now generally available in the Red Hat container registry.
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A new version of Migration Toolkit for Containers (MTC) is now available.
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A new satellite/iop-vulnerability-engine-rhel9 container image is now available as a Technology Preview in the Red Hat container registry.
Red Hat Security Advisory: Red Hat AI Inference Server Model Optimization Tools 3.2.2 (CUDA)
Red Hat AI Inference Server Model Optimization Tools 3.2.2 (CUDA) is now available.
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> RED HAT SEVERITY ASSESSMENT

THREAT SEVERITY
Important

> GITHUB SECURITY ADVISORY

GHSA-38jv-5279-wg99 HIGH

Decompression-bomb safeguards bypassed when following HTTP redirects (streaming API)

AFFECTED PACKAGES:
PIP / urllib3
>= 1.22, < 2.6.3
Fixed in: 2.6.3

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)

AFFECTED PACKAGES:
Unknown / Unknown
ALIASES:
GHSA-38jv-5279-wg99, PYSEC-2026-1996

> HISTORIQUE DES MODIFICATIONS

Première apparition
07/01/2026 22:15
Source: NVD
📊 ENRICHISSEMENT 01/11/2026 06:58
CWE
Champ modifié: Description CWE
Ancienne valeur:
CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) - The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a lar...
Nouvelle valeur:
CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) - The product does not handle or incorrectly handles a compressed input with a very high compression ratio t...
📊 ENRICHISSEMENT 01/02/2026 06:44
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) - The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a lar...
📊 ENRICHISSEMENT 19/01/2026 17:38
CVEPROJECT
Champ modifié: CVE Project
Ancienne valeur:
Non
Nouvelle valeur:
Oui
📊 ENRICHISSEMENT 11/01/2026 04:01
REDHAT
Champ modifié: Sévérité Red Hat
Ancienne valeur:
N/A
Nouvelle valeur:
{ "threat_severity": "Important", "severity_scale": null }
📊 ENRICHISSEMENT 11/01/2026 04:01
REDHAT
Champ modifié: Red Hat
Ancienne valeur:
Non
Nouvelle valeur:
Oui
Total des modifications: 5 Dernière mise à jour: 1 week ago

> REFERENCES

https://github.com/urllib3/urllib3/commit/8864ac407bba8607950025e0979c4c69bc7abc...
https://github.com/urllib3/urllib3/security/advisories/GHSA-38jv-5279-wg99
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