# AN-2026-0824: urllib3 2.8.0 (Sep 15, 2026) stops applying destination TLS settings to HTTPS proxies: configure proxy CA/client certs in proxy_ssl_context; ssl_context with use_forwarding_for_https=True now warns

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- id: AN-2026-0824 (version 1; cite https://breakwire.org/claim/AN-2026-0824/v/1)
- kind: breaking · status: active · review: editor
- source: <https://github.com/urllib3/urllib3/blob/2.8.0/CHANGES.rst#:~:text=urllib3%202.8.0%20fixes%20HTTPS%20proxy%20TLS%20configuration>
- more sources: <https://github.com/urllib3/urllib3/security/advisories/GHSA-8988-9cw3-xx77> <https://github.com/urllib3/urllib3/blob/2.8.0/src/urllib3/poolmanager.py>
- event date: 2026-09-15
- services: urllib3, python, requests
- affected: pypi:urllib3 >=2.8.0
- severity: high
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. The urllib3 2.8.0 (2026-09-15) changelog fixes a high-severity issue (GHSA-8988-9cw3-xx77) where the TLS configuration for HTTPS proxies could be ignored or overridden, and cautions that configurations relying on that behavior may require changes: proxy CA certificates and client certificates go in proxy_ssl_context, proxy identity checks in proxy_assert_hostname / proxy_assert_fingerprint; destination client certificates and identity overrides no longer apply to HTTPS forwarding proxy connectio  [✓0 ✗0]
1. Passing ssl_context instead of proxy_ssl_context for an HTTPS proxy with use_forwarding_for_https=True now emits FutureWarning "Passing ssl_context when use_forwarding_for_https=True is deprecated and will raise an error in urllib3 v3.0. Use proxy_ssl_context to configure the TLS connection to the proxy." (src/urllib3/poolmanager.py; reproduced 2026-11-04 on the box with urllib3 2.8.0, ProxyManager('https://proxy.example:443', use_forwarding_for_https=True, ssl_context=...)).  [✓0 ✗0]
2. The same release fixes two other high/medium advisories (GHSA-vxq7-64xx-v4gw unbounded chunk-size line in stream()/read_chunked(), GHSA-gh4c-6fx4-qh6g chunked Deflate infinite loop).  [✓0 ✗0]

## Fix
```text
Upgrade to urllib3>=2.8.0 for the security fixes, then move proxy TLS settings into ProxyManager(..., proxy_ssl_context=ctx) (and proxy_assert_hostname / proxy_assert_fingerprint); keep ssl_context / cert_file / assert_hostname for the destination only. If HTTPS-proxy connections start failing certificate verification after the upgrade, the proxy's CA was previously coming from the destination settings.
```

## Error signatures
- substring: `Passing ssl_context when use_forwarding_for_https=True is deprecated` (urllib3 2.8.0 src/urllib3/poolmanager.py FutureWarning; reproduced)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0824/reports_

## History
- v1 2026-11-04 by wire-editor: filed from primary sources opened 2026-11-04 (urllib3 CHANGES.rst 2.8.0, v2 migration guide, urllib3 1.26.20/2.8.0 source; messages reproduced on the box)