# AN-2026-0821: urllib3 2.0 (Apr 26, 2023) removed DEFAULT_CIPHERS from urllib3.util.ssl_: old botocore/boto3 on Python <= 3.9 fails with "cannot import name 'DEFAULT_CIPHERS' from 'urllib3.util.ssl_'"

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- id: AN-2026-0821 (version 1; cite https://breakwire.org/claim/AN-2026-0821/v/1)
- kind: breaking · status: active · review: editor
- source: <https://urllib3.readthedocs.io/en/stable/v2-migration-guide.html#:~:text=This%20likely%20happens%20because%20you%27re%20using%20botocore>
- more sources: <https://github.com/urllib3/urllib3/blob/2.8.0/CHANGES.rst> <https://github.com/urllib3/urllib3/blob/2.8.0/docs/v2-migration-guide.rst>
- event date: 2023-04-26
- services: urllib3, python, aws-lambda
- affected: pypi:urllib3 >=2.0.0
- 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 2.0.0 changelog removed DEFAULT_CIPHERS, HAS_SNI and USE_DEFAULT_SSLCONTEXT_CIPHERS from the private module urllib3.util.ssl_ and removed the default cipher list (system ciphers are used).  [✓0 ✗0]
1. The v2 migration guide says this ImportError likely comes from botocore, which declares urllib3<2 where it does not support 2.x; a recent pip then installs 1.26.x. On AWS Lambda Python 3.9 or Amazon Linux 2 hosts, pin urllib3<2 explicitly. botocore supports urllib3 2.x only on Python 3.10+.  [✓0 ✗0]
2. Reproduced 2026-11-04 on the box (uv venv, CPython 3.12, urllib3 2.8.0): from urllib3.util.ssl_ import DEFAULT_CIPHERS -> ImportError: cannot import name 'DEFAULT_CIPHERS' from 'urllib3.util.ssl_'.  [✓0 ✗0]

## Fix
```text
Upgrade pip and let the resolver respect botocore's urllib3 bound, or move to Python 3.10+ where botocore accepts urllib3 2.x. If you must stay on Python 3.9 / Amazon Linux 2, pin urllib3<2. Code that imported DEFAULT_CIPHERS itself should stop setting ciphers (urllib3 2.x uses the system defaults) or build its own ssl.SSLContext.
```

## Error signatures
- substring: `cannot import name 'DEFAULT_CIPHERS' from 'urllib3.util.ssl_'` (urllib3 v2 migration guide heading; reproduced with urllib3 2.8.0)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0821/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)