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TI-2026-64263 Aliases CVE-2026-97688GHSA-gh4c-6fx4-qh6g

urllib3: Chunked Deflate streaming can enter an infinite loop

Priority LOW 36CWE-835Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Partial Red Hat: 5 fixed, 1 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-835.

Summary

urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00292 21st percentileScored 2026-11-07
Fix Partial urllib3 (urllib3): 2.8.0urllib3 (PyPI): 2.8.0Red Hat: 15 advisoriesRed Hat: 5 fixed, 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
python-pillowurllib32.6.2 to before 2.8.02.8.0Patch availableCNA
—urllib3 (PyPI)2.6.2 to before 2.8.02.8.0Patch availableGHSA-gh4c-6fx4-qh6g
  • urllib3 Vendorpython-pillow Affected 2.6.2 to before 2.8.0 Fixed in 2.8.0 Patch available CNA
  • urllib3 (PyPI) Vendor— Affected 2.6.2 to before 2.8.0 Fixed in 2.8.0 Patch available GHSA-gh4c-6fx4-qh6g

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:*2.6.2 to before 2.8.0Vulnerablepython-pillow
  • cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:* Versions 2.6.2 to before 2.8.0 Vulnerable ·python-pillow

Remediation

  • Fix · CNA urllib3 (urllib3) Fixed in 2.8.0
  • Fix · GHSA-gh4c-6fx4-qh6g urllib3 (PyPI) Fixed in 2.8.0 Advisory →

Red Hat 15 advisories

  • RHSA-2026:92452 Released 2026-10-29 · Red Hat rating Critical
    Red Hat Enterprise Linux AI 3.5.2 enhancement update
    • Red Hat Enterprise Linux AI 3.5 registry.redhat.io/rhelai3/bootc-aws-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-rocm-rhel9 +3
  • RHSA-2026:92449 Released 2026-10-29 · Red Hat rating Critical
    Red Hat Enterprise Linux AI 3.5.2 enhancement update
    • Red Hat Enterprise Linux AI 3.5 registry.redhat.io/rhelai3/disk-image-cuda-rhel9
  • RHSA-2026:90440 Released 2026-10-26 · Red Hat rating Important
    Red Hat Enterprise Linux AI 3.4.6 security update
    • Red Hat Enterprise Linux AI 3.4 registry.redhat.io/rhelai3/bootc-aws-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-rocm-rhel9 +3
Show 12 more Red Hat advisories
  • RHSA-2026:90432 Released 2026-10-26 · Red Hat rating Important
    Red Hat Enterprise Linux AI 3.4.6 security update
    • Red Hat Enterprise Linux AI 3.4 registry.redhat.io/rhelai3/disk-image-cuda-rhel9
  • RHSA-2026:83121 Released 2026-10-14 · Red Hat rating Important
    Red Hat AI Inference 3.4.6 (rocm)
    • Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-rocm-rhel9
  • RHSA-2026:83120 Released 2026-10-14 · Red Hat rating Important
    Red Hat AI Inference 3.4.6 (cuda)
    • Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-cuda-rhel9
  • RHSA-2026:83116 Released 2026-10-14 · Red Hat rating Important
    Red Hat AI Inference Model Optimization Tools 3.4.6 (cuda)
    • Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/model-opt-cuda-rhel9
  • RHSA-2026:83114 Released 2026-10-14 · Red Hat rating Important
    Red Hat AI Inference 3.4.6 (spyre)
    • Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-spyre-rhel9
  • RHSA-2026:83112 Released 2026-10-14 · Red Hat rating Important
    Red Hat AI Inference 3.4.6 (cpu)
    • Red Hat AI Inference Server 3.4 registry.redhat.io/rhaii/vllm-cpu-rhel9
  • RHSA-2026:82415 Released 2026-10-13 · Red Hat rating Critical
    Red Hat AI Inference 3.5.2 (cpu)
    • Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-cpu-rhel9
  • RHSA-2026:82371 Released 2026-10-13 · Red Hat rating Critical
    Red Hat AI Inference 3.5.2 (spyre)
    • Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-spyre-rhel9
  • RHSA-2026:82368 Released 2026-10-13 · Red Hat rating Critical
    Red Hat AI Inference 3.5.2 (cuda)
    • Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-cuda-rhel9
  • RHSA-2026:82061 Released 2026-10-13 · Red Hat rating Critical
    Red Hat AI Inference Tech Preview 3.5.2 (Gaudi)
    • Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-gaudi-rhel9
  • RHSA-2026:82059 Released 2026-10-13 · Red Hat rating Critical
    Red Hat AI Inference 3.5.2 (ROCm)
    • Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-rocm-rhel9
  • RHSA-2026:69612 Released 2026-09-21 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images python-urllib3-2.8.0-1.hum1@src, python3-urllib3+brotli-2.8.0-1.hum1@noarch@public-hummingbird-aarch64-rpms, python3-urllib3+brotli-2.8.0-1.hum1@noarch@public-hummingbird-x86_64-rpms +8

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet: Fix deferred
Red Hat AI Inference Server 3.4Fixed RHSA-2026:83112, RHSA-2026:83114, RHSA-2026:83116, RHSA-2026:83120, RHSA-2026:83121
Red Hat AI Inference Server 3.5Fixed RHSA-2026:82059, RHSA-2026:82061, RHSA-2026:82368, RHSA-2026:82371, RHSA-2026:82415
Red Hat Enterprise Linux AI 3.4Fixed RHSA-2026:90432, RHSA-2026:90440
Red Hat Enterprise Linux AI 3.5Fixed RHSA-2026:92449, RHSA-2026:92452
Red Hat Hardened ImagesFixed RHSA-2026:69612
Not affected: 1 product
  • Red Hat Hardened Images

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-97688
  2. 2026-10-03 Alias added: GHSA-gh4c-6fx4-qh6g
  3. 2026-10-13 Fix available: RHSA-2026:82061 · Red Hat
  4. 2026-10-13 Fix available: RHSA-2026:82059 · Red Hat
  5. 2026-10-13 Fix available: Red Hat AI Inference Server 3.5 · Red Hat
  6. 2026-10-13 CVSS score added · NVD
  7. 2026-10-14 Fix available: RHSA-2026:82368 · Red Hat
  8. 2026-10-14 Fix available: RHSA-2026:82415 · Red Hat
  9. 2026-10-14 Fix available: RHSA-2026:82371 · Red Hat
  10. 2026-10-16 Fix available: RHSA-2026:83112 · Red Hat
  11. 2026-10-16 Fix available: RHSA-2026:83116 · Red Hat
  12. 2026-10-16 Fix available: RHSA-2026:83114 · Red Hat
  13. 2026-10-16 Fix available: RHSA-2026:83120 · Red Hat
  14. 2026-10-16 Fix available: RHSA-2026:83121 · Red Hat
  15. 2026-10-16 Fix available: Red Hat AI Inference Server 3.4 · Red Hat
  16. 2026-10-30 Fix available: RHSA-2026:92452 · Red Hat
  17. 2026-10-30 Fix available: RHSA-2026:92449 · Red Hat
  18. 2026-10-30 Fix available: RHSA-2026:90432 · Red Hat
  19. 2026-10-30 Fix available: RHSA-2026:90440 · Red Hat
  20. 2026-10-30 Fix available: Red Hat Enterprise Linux AI 3.4, Red Hat Enterprise Linux AI 3.5 · Red Hat
  21. 2026-11-06 Affected versions changed · Red Hat

References

Patch 1

Advisory 2

Other 2

  • TI-2026-17326 urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API) CVSS 4.0HIGH 8.9
  • TI-2018-14221 urllib3 before version 1.23 does not remove the Authorization HTTP header when following… CVSS 3.0CRITICAL 9.8
  • TI-2025-40854 urllib3 allows an unbounded number of links in the decompression chain CVSS 4.0HIGH 8.9
  • TI-2026-32373 urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API CVSS 4.0HIGH 8.9
  • TI-2025-40898 urllib3 Streaming API improperly handles highly compressed data CVSS 4.0HIGH 8.9
  • TI-2021-12905 An issue was discovered in urllib3 before 1.26.5. CVSS 3.1HIGH 7.5
See all 21 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences