Vulnerability in Pyca Pyopenssl
CVE-2026-27448
pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 0.14.0 and prior to version 26.0.0, if a user provided callback to `set_tlsext_servername_callback` raised an unhandled exception, this would result in a connection being accepted. If a user was relying on this callback for any security-sensitive behavior, this could allow bypassing it. Starting in version 26.0.0, unhandled exceptions now result in rejecting the connection.
EPSS: 0.002 (15.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
Affected products
- Pyca Pyopenssl — versions >= 0.14.0, < 26.0.0
- Pyopenssl
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-27448?
- CVE-2026-27448 is a medium-severity vulnerability in Pyca Pyopenssl, classified under CWE-636. CVSS score: 5.3/10. Published 2026-03-18.
- How severe is CVE-2026-27448?
- Medium severity. CVSS v3 base score is 5.3 out of 10.