CVE-2026-19445
Use-after-free of a server-side SSLContext when sni_callback switches contexts
Description
A remote, unauthenticated TLS client can make a server crash or call through a freed pointer if its sni_callback assigns a different context to SSLSocket.context (the documented way to select a certificate per server name) and nothing else keeps the original ssl.SSLContext alive. Typical cases are servers that create an SSLContext per connection or replace it while connections are open; servers that wrap their listening socket with it are not affected. Mitigation: keep a reference to every SSLContext that sets sni_callback for the lifetime of the server. TLS clients are not affected.
INFO
Published Date :
Sept. 30, 2026, 5:16 p.m.
Last Modified :
Sept. 30, 2026, 11:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-19445
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | CRITICAL | 28c92f92-d60d-412d-b760-e73465c3df22 | ||||
| CVSS 4.0 | CRITICAL | [email protected] |
Solution
- Keep references to all SSLContexts with sni_callback.
- Do not replace SSLContext while connections are open.
- Avoid creating SSLContext per connection.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-19445.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-19445 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-19445
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-19445 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-19445 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Sep. 30, 2026
Action Type Old Value New Value Added Affected Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/19xxx/CVE-2026-19445.json">CVE-2026-19445</a> -
CVE Modified by [email protected]
Sep. 30, 2026
Action Type Old Value New Value Added Affected Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/19xxx/CVE-2026-19445.json">CVE-2026-19445</a> Added Reference https://github.com/python/cpython/commit/34a53dce8174da2fceb12fe084a4def02a10053d Added Reference https://github.com/python/cpython/commit/46133cd57d309652139ada74014aca7665ac552b Added Reference https://github.com/python/cpython/commit/63fab143d94cafae71850831acfb52041ba44af7 Added Reference https://github.com/python/cpython/commit/cd7e51e7d4563866fbaa1e2521ae69b45daf3698 Added Reference https://github.com/python/cpython/commit/d8717ed01717a9641686e6e6f83f0ab8af235e2c -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Sep. 30, 2026
Action Type Old Value New Value Added Reference http://www.openwall.com/lists/oss-security/2026/09/30/17 -
New CVE Received by [email protected]
Sep. 30, 2026
Action Type Old Value New Value Added Description A remote, unauthenticated TLS client can make a server crash or call through a freed pointer if its sni_callback assigns a different context to SSLSocket.context (the documented way to select a certificate per server name) and nothing else keeps the original ssl.SSLContext alive. Typical cases are servers that create an SSLContext per connection or replace it while connections are open; servers that wrap their listening socket with it are not affected. Mitigation: keep a reference to every SSLContext that sets sni_callback for the lifetime of the server. TLS clients are not affected. Added CVSS V4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-416 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/19xxx/CVE-2026-19445.json">CVE-2026-19445</a> Added Reference https://github.com/python/cpython/issues/156293 Added Reference https://github.com/python/cpython/pull/158504 Added Reference https://mail.python.org/archives/list/[email protected]/thread/QMQIUQB6WGGC3MI7I3WKQXOYOBDSPPS3/