# CVE-2026-19445: Python use-after-free in SSL server-side context with sni_callback

Source: https://junglewise.ai/threats/cve-2026-19445-a-remote-unauthenticated-tls-client-can-make-a-server-crash-or  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-30. Updated: 2026-09-30  
License: CC BY 4.0 with a link back

CVE-2026-19445 · Severity: info · Published 2026-09-30

Python's SSL module has a use-after-free vulnerability in server implementations that reassign SSL contexts during TLS connections using the sni_callback mechanism for certificate selection. An unauthenticated remote attacker can crash the server or execute arbitrary code by triggering access to a freed memory region. This affects servers that create or replace SSL contexts per connection rather than wrapping a listening socket with a single shared context.

Technologies: [Python CPython](https://junglewise.ai/threats/technologies/python-cpython). Vendors: [Python](https://junglewise.ai/threats/vendors/python).

## Quick answers

**Is CVE-2026-19445 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19445 being exploited in the wild.

**How severe is CVE-2026-19445?** Informational severity, published 30 September 2026.

**Which products and versions are affected?** Python CPython 3.10, 3.11, 3.12, 3.13, 3.14, 3.15.

**Is there a fix for CVE-2026-19445?** A patch was published on 2026-09-30. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-19445 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-19445?** Check whether you run Python CPython 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.

## Technical details

A use-after-free flaw exists in the Python ssl module when an SNI callback handler assigns a different SSLContext to SSLSocket.context without keeping a reference to the original context. The vulnerability is triggered by an unauthenticated remote TLS client and allows reading from or writing to freed memory. The issue affects server-side socket implementations only; typical vulnerable patterns are per-connection context creation or runtime context replacement.

## Affected products

- Python CPython 3.10, 3.11, 3.12, 3.13, 3.14, 3.15

## Timeline

- 2026-09-30: disclosed
- 2026-09-30: patched

## References

- [https://github.com/python/cpython/issues/156293](https://github.com/python/cpython/issues/156293)
- [https://github.com/python/cpython/pull/158504](https://github.com/python/cpython/pull/158504)

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