[ CVE-2026-97688 · Published 29 Sep 2026 ]
urllib3: Chunked Deflate streaming can enter an infinite loop
[ Description ]Official description
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.
[ Fixes ]Fixes and patches
- urllib3 2.8.0Fixed version · GitHub Advisories · pip package urllib3: upgrade to 2.8.0 or later (affected >= 2.6.2, < 2.8.0)
- Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD
[ Advisories ]Government CERT advisories
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CERT-FRCERTFR-2026-AVI-1249
Multiple vulnerabilities in VMware products Translated from French
Multiple vulnerabilities have been discovered in VMware products. They allow an attacker to cause a security problem not specified by the vendor.
[ Packages ]Affected open-source packages
- urllib3 pipAffected >= 2.6.2, < 2.8.0 · fixed in 2.8.0 · GHSA-gh4c-6fx4-qh6g