CVE-2026-19445: Use-after-free of a server-side SSLContext when sni_callback switches contexts

Versions reported by the vendor

Affected version ranges reported by the assigning authority (PSF). Independent of NVD's CPE analysis and usually ahead of it.

• Python Software Foundation CPython

  • before 3.10.22affected · python
  • 3.11.0 and later · before 3.11.17affected · python
  • 3.12.0 and later · before 3.12.15affected · python
  • 3.13.0 and later · before 3.13.16affected · python
  • 3.14.0 and later · before 3.14.8affected · python
  • 3.15.0a1 and later · before 3.15.0rc3affected · python

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Other highest-scoring records for the same primary product.

• CVE-2026-115557Distrust compromised intermediate certificates in ssl module
  37Monitor
• CVE-2025-4517Arbitrary writes via tarfile realpath overflow
  37Monitor
• CVE-2026-6100Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure
  36Monitor

Published before and after this one in the same product

• ← EarlierCVE-2026-82049Sep 14, 2026 · tarfile extraction filters allow file modification and content disclosure via hard link to symlink
  33Monitor
• ← EarlierCVE-2026-12345Sep 29, 2026 · Race condition in tempfile.TemporaryDirectory cleanup allows deleting files outside the temporary directory
  23Monitor
• Later →CVE-2026-19553Sep 30, 2026 · SSLContext.wrap_bio() missing validation of server_hostname parameter
  30Monitor

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

1free(dev->buf);2/* ... another thread is still running ... */3process(dev->buf);

1lock(&dev->lock);2free(dev->buf);3dev->buf = NULL;4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.