🛡️ CVE-2026-27448 — pyopenssl

🟢 CVSS 2.0 — Low ✅ No Known Exploit CWE-636 OSV
2.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. Rated impact: confidentiality none, integrity low, availability none.

Affected software

CVE-2026-27448 is recorded against 1 package.

  • pyopenssl (from 0.14.0 up to 26.0.0)

Timeline and source

Published on 16 March 2026 and last revised on 13 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Package)
github.com (Web)

CVE-2026-27448 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity LOW
CVSS Score 2.0
CVSS Vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U
CWE CWE-636
Public Exploit ✅ No
Source OSV
Published 2026-03-16
Updated 2026-08-12
Modified 2026-07-13

Affected Packages

Software From version Fixed in
pyopenssl 0.14.0 26.0.0

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