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Vulnerabilities

Vulnerability · CVE-2026-97688

urllib3 is an HTTP client library for Python.

Published Sep 29, 2026 · catalog updated Oct 14, 2026 · Canonical Ubuntu

Check if you run it

No confirmed exploitation is on record for CVE-2026-97688. EPSS is 0.29%. Act only if a listed version of Canonical Ubuntu is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.29%
Remediation
Advisory link
Affected products
Ubuntu:22.04:LTS python-urllib3 · Ubuntu:24.04:LTS python-urllib3 · Ubuntu:Pro:14.04:LTS python-pip · Ubuntu:Pro:14.04:LTS python-urllib3 · Ubuntu:Pro:16.04:LTS python-pip · Ubuntu:Pro:16.04:LTS python-urllib3

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • 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

How to fix CVE-2026-97688

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-97688. EPSS is 0.29%. Act only if a listed version of Canonical Ubuntu is installed.

Which versions are affected?

Compare what you have installed with 1.26.5-1~exp1, 1.26.5-1~exp1ubuntu0.1, 1.26.5-1~exp1ubuntu0.2, 1.26.16-1, 1.26.18-1, 2.0.7-1, 1.4.1-2, 1.5.4-1, 1.5.4-1ubuntu1, 1.6-2, 1.7.1-1, 1.7.1-1build1, 1.5.6-7ubuntu1, 1.5.6-7ubuntu2, 8.0.2-7, 1.11-1, 1.12-1, 1.13.1-1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.29%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Ubuntu security

Code

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

Timeline

Detection, updates, and resolution for this record.

  1. 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

  2. Oct 14, 2026 · OpenSSF OSV / OSV Scanner

    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

Sources

  • CVE.orgVulnerability recordCVE-2026-97688

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-97688

    30-day exploitation probability 0.3%

    first.org
  • OpenSSF OSV / OSV ScannerPackage 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

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.