Description
urllib3 is an HTTP client library for Python. From 1.26.0 until 2.8.0, the proxy_ssl_context, proxy_assert_hostname, proxy_assert_fingerprint, ssl_context, cert_reqs, verify_mode, use_forwarding_for_https=True, and CERT_NONE configuration paths fail to remain separated because target-server TLS settings are incorrectly applied to the HTTPS proxy connection. The trigger is that an application uses an HTTPS proxy and configures target-server TLS settings that must remain separate from the proxy TLS handshake, including HTTPS forwarding with target-specific identity or credentials. Applying cert_reqs=CERT_NONE can overwrite proxy_ssl_context.verify_mode in place, and the mutation persists so later connections reusing the same context may connect to the HTTPS proxy without certificate verification. The attack mechanism is that an attacker intercepts and impersonates the HTTPS proxy after the effective proxy policy accepts the attacker's certificate. The impact is that the attacker can observe or modify forwarded traffic or receive a target TLS client certificate, while CONNECT tunneling still preserves the separate end-to-end target TLS connection. This issue is fixed in version 2.8.0.
Published: 2026-09-29
Score: 7.6 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-8988-9cw3-xx77 urllib3: HTTPS proxy TLS configuration may be ignored or overridden
History

Wed, 30 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Wed, 30 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'}

threat_severity

Important


Tue, 29 Sep 2026 18:30:00 +0000

Type Values Removed Values Added
First Time appeared Urllib3
Urllib3 urllib3
Vendors & Products Urllib3
Urllib3 urllib3

Tue, 29 Sep 2026 15:45:00 +0000

Type Values Removed Values Added
Description urllib3 is an HTTP client library for Python. From 1.26.0 until 2.8.0, the proxy_ssl_context, proxy_assert_hostname, proxy_assert_fingerprint, ssl_context, cert_reqs, verify_mode, use_forwarding_for_https=True, and CERT_NONE configuration paths fail to remain separated because target-server TLS settings are incorrectly applied to the HTTPS proxy connection. The trigger is that an application uses an HTTPS proxy and configures target-server TLS settings that must remain separate from the proxy TLS handshake, including HTTPS forwarding with target-specific identity or credentials. Applying cert_reqs=CERT_NONE can overwrite proxy_ssl_context.verify_mode in place, and the mutation persists so later connections reusing the same context may connect to the HTTPS proxy without certificate verification. The attack mechanism is that an attacker intercepts and impersonates the HTTPS proxy after the effective proxy policy accepts the attacker's certificate. The impact is that the attacker can observe or modify forwarded traffic or receive a target TLS client certificate, while CONNECT tunneling still preserves the separate end-to-end target TLS connection. This issue is fixed in version 2.8.0.
Title urllib3: HTTPS proxy TLS configuration may be ignored or overridden
Weaknesses CWE-295
CWE-440
References
Metrics cvssV4_0

{'score': 7.6, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-30T20:11:09.721Z

Reserved: 2026-09-24T21:43:37.208Z

Link: CVE-2026-97687

cve-icon Vulnrichment

Updated: 2026-09-30T19:48:58.509Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-29T16:17:18.517

Modified: 2026-09-30T21:17:19.473

Link: CVE-2026-97687

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-29T15:30:27Z

Links: CVE-2026-97687 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-30T01:30:17Z

Weaknesses
  • CWE-295

    Improper Certificate Validation

  • CWE-440

    Expected Behavior Violation