Description
The X509Extension in pyOpenSSL before 0.13.1 does not properly handle a '\0' character in a domain name in the Subject Alternative Name field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | pyopenssl | 0.13-2.1 | — |
| Debian 13 | pyopenssl | 0.13-2.1 | — |
| Debian 12 | pyopenssl | 0.13-2.1 | — |
| Debian 7 | pyopenssl | 0.13-2+deb7u1 | DSA-2763-1 |
| Debian 6.0 | pyopenssl | 0.10-1+squeeze1 | DSA-2763-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | python-pyOpenSSL | 24.1.0-1.2 | openSUSE-SU-2026:11470-1, openSUSE-SU-2024:14154-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | pyopenssl | < 0.13.1 | 0.13.1 | GHSA-6748-36qp-fx6r |
Advisories 3
- openSUSE-SU-2026:11470-1 python313-pyOpenSSL-26.4.0-1.1 on GA media SUSE / openSUSE Security Updates · Aug 7, 2026
- DSA-2763-1 pyopenssl - hostname check bypassing Debian Security (DSA / DLA) · Mar 9, 2026
- openSUSE-SU-2024:14154-1 python310-pyOpenSSL-24.1.0-1.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
References
- DSA-2763 vendor-advisory
- [pyOpenSSL-Users] 20130904 pyOpenSSL 0.13.1 mailing-list
- https://bugzilla.redhat.com/show_bug.cgi?id=1005325
- openSUSE-SU-2013:1648 vendor-advisory
- [oss-security] 20130906 Re: CVE request: pyOpenSSL hostname check bypassing vulnerability mailing-list
- USN-1965-1 vendor-advisory