CVE-2026-97688

urllib3 is an HTTP client library for Python.

Published Sep 29, 2026 · corrected/updated Oct 14, 2026 · Canonical Ubuntu · evidence confidence high

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.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-97688 is a unknown public vulnerability record for Canonical Ubuntu. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether Canonical Ubuntu is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: python-urllib3 (1.26.5-1~exp1, 1.26.5-1~exp1ubuntu0.1, 1.26.5-1~exp1ubuntu0.2); python-urllib3 (1.26.16-1, 1.26.18-1, 2.0.7-1); python-pip (1.4.1-2, 1.5.4-1, 1.5.4-1ubuntu1); python-urllib3 (1.6-2, 1.7.1-1, 1.7.1-1build1). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: no CVSS/EPSS yet. It is not currently listed in the CISA Known Exploited catalog. Sources contributing to this record: cve_org, osv, ubuntu. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

Exploitation evidence
Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Technology hubs

Ubuntu

Code

The project this record applies to. Exploit listings stay in References.

Repository · github.com

Timeline

Detection, updates, and resolution for this record.

Oct 14, 2026 · Ubuntu Security Notices
Detected
Yu-Fu Fu, Seth Larson and Yonatan Magier discovered that urllib3 did not correctly handle certain certificate validations. An attacker could possibly use this issue to observe or modify forwarded traffic. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-97687) Martin Desrumaux discovered that urllib3 did not correctly handle decoding certain deflate responses. An attacker could possibly use th
Oct 14, 2026 · OSV.dev
Updated
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 pos

Affected

Ubuntu:22.04:LTS python-urllib31.26.5-1~exp1, 1.26.5-1~exp1ubuntu0.1, 1.26.5-1~exp1ubuntu0.2
Ubuntu:24.04:LTS python-urllib31.26.16-1, 1.26.18-1, 2.0.7-1
Ubuntu:Pro:14.04:LTS python-pip1.4.1-2, 1.5.4-1, 1.5.4-1ubuntu1
Ubuntu:Pro:14.04:LTS python-urllib31.6-2, 1.7.1-1, 1.7.1-1build1
Ubuntu:Pro:16.04:LTS python-pip1.5.6-7ubuntu1, 1.5.6-7ubuntu2, 8.0.2-7
Ubuntu:Pro:16.04:LTS python-urllib31.11-1, 1.12-1, 1.13.1-1
Ubuntu:Pro:18.04:LTS python-pip9.0.1-2, 9.0.1-2.3~ubuntu1, 9.0.1-2.3~ubuntu1.18.04.1
Ubuntu:Pro:18.04:LTS python-urllib31.21.1-1, 1.22-1, 1.22-1ubuntu0.18.04.1
Ubuntu:Pro:20.04:LTS python-pip18.1-5, 18.1-5build1, 18.1-5ubuntu1
Ubuntu:Pro:20.04:LTS python-urllib31.24.1-1ubuntu1, 1.24.1-1ubuntu2, 1.25.8-1
Ubuntu:Pro:22.04:LTS python-pip20.3.4-4, 21.3.1+dfsg-3, 22.0.2+dfsg-1
Ubuntu:Pro:24.04:LTS python-pip23.2+dfsg-1, 23.3+dfsg-1, 24.0+dfsg-1

Sources

CVE.orgVulnerability recordCVE-2026-97688
Official CVE identifier
cve.org
OSV.devPackage advisoryUBUNTU-CVE-2026-97688
osv.dev
Ubuntu Security NoticesVendor advisoryCVE-2026-97688
Yu-Fu Fu, Seth Larson and Yonatan Magier discovered that urllib3 did not correctly handle certain certificate validations. An attacker could possibly use this issue to observe or modify forwarded traffic. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-97687) Martin Desrumau
ubuntu.com