Summary
pyOpenSSL allows TLS connection bypass via unhandled callback exception in settlsextservername_callback
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.
Unhandled exceptions now result in rejecting the connection.
Credit to Leury Castillo for reporting this issue.
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-27448? CVE-2026-27448 is a low-severity security vulnerability in pyopenssl (pip), affecting versions >= 0.14.0, < 26.0.0. It is fixed in 26.0.0.
- Which versions of pyopenssl are affected by CVE-2026-27448? pyopenssl (pip) versions >= 0.14.0, < 26.0.0 is affected.
- Is there a fix for CVE-2026-27448? Yes. CVE-2026-27448 is fixed in 26.0.0. Upgrade to this version or later.
- Is CVE-2026-27448 exploitable, and should I be worried? Whether CVE-2026-27448 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-27448 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-27448? Upgrade
pyopensslto 26.0.0 or later.