# CVE-2026-97687: urllib3 HTTPS proxy TLS settings isolation

Source: https://junglewise.ai/threats/cve-2026-97687-urllib3-is-an-http-client-library-for-python-from-1-26-0-until-2  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-29. Updated: 2026-09-29  
License: CC BY 4.0 with a link back

CVE-2026-97687 · Severity: high · CVSS 4 · Published 2026-09-29

urllib3 is a Python HTTP client library used by many applications to make web requests through proxies. When an application connects through an HTTPS proxy with specific security settings, those settings can incorrectly leak to the target server connection, allowing an attacker who intercepts the proxy to eavesdrop on or modify traffic between the application and its intended destination.

Technologies: [urllib3 (PyPI)](https://junglewise.ai/threats/technologies/urllib3), [Urllib3](https://junglewise.ai/threats/technologies/urllib3-urllib3). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi), [Urllib3](https://junglewise.ai/threats/vendors/urllib3).

## Quick answers

**Is CVE-2026-97687 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-97687 being exploited in the wild.

**How severe is CVE-2026-97687?** High severity, with a CVSS score of 4, published 29 September 2026.

**Which products and versions are affected?** urllib3 (PyPI) >= 1.26.0, < 2.8.0, ECOSYSTEM:introduced=1.26.0,fixed=2.8.0; Urllib3 1.26.0 to 2.7.x.

**Is there a fix for CVE-2026-97687?** Yes. urllib3 (PyPI): upgrade to 2.8.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-97687 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-97687?** Check whether you run urllib3 (PyPI) or Urllib3 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- urllib3 (PyPI): upgrade to 2.8.0 or later

  ```sh
  pip install "urllib3>=2.8.0"
  ```


## Technical details

Target-server TLS settings (cert_reqs, verify_mode, ssl_context, and hostname assertions) are incorrectly applied to the HTTPS proxy TLS handshake instead of remaining isolated, due to in-place mutation of shared ssl_context objects. An attacker positioned to intercept the HTTPS proxy connection can present a fake certificate that would be rejected if settings were properly enforced. The fix in version 2.8.0 isolates proxy TLS configuration from target TLS settings, preventing the leakage and in-place mutations.

## Affected products

- urllib3 urllib3 1.26.0 to 2.7.x

## Identifiers

- CVE-2026-97687
- GHSA-8988-9cw3-xx77
- PYSEC-2026-4175

## Timeline

- 2026-09-29: disclosed
- 2026-07-29: patched: Fix committed; released in version 2.8.0

## References

- [https://github.com/urllib3/urllib3/commit/07408cec79d1856d81bb42c74a904a24fdb9e465](https://github.com/urllib3/urllib3/commit/07408cec79d1856d81bb42c74a904a24fdb9e465)
- [https://github.com/urllib3/urllib3/commit/b6447295fff7b38fdffc67e0df9712d60cef3cc3](https://github.com/urllib3/urllib3/commit/b6447295fff7b38fdffc67e0df9712d60cef3cc3)

## Related threats

- [urllib3 HTTP client unbounded memory allocation in chunked transfer](https://junglewise.ai/threats/cve-2026-97689-urllib3-is-an-http-client-library-for-python-from-1-10-3-until-2)
- [urllib3 infinite loop in Deflate decoder](https://junglewise.ai/threats/cve-2026-97688-urllib3-is-an-http-client-library-for-python-from-2-6-2-until-2-8)
- [PYSEC-2026-1997 - urllib3 does not control redirects in browsers and Node.js](https://junglewise.ai/threats/cve-2025-50182-urllib3-does-not-control-redirects-in-browsers-and-node-js)
- [PYSEC-2026-1999 - urllib3 redirects are not disabled when retries are disabled on PoolManager instantiation](https://junglewise.ai/threats/cve-2025-50181-urllib3-redirects-are-not-disabled-when-retries-are-disabled-on)
- [PYSEC-2026-1995 - urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects](https://junglewise.ai/threats/cve-2024-37891-urllib3-proxy-authorization-header-leak-in-cross-origin-redirects)