CVE-2013-4314: The X509Extension in pyOpenSSL before 0.13.1 does not properly handle a '\0' character in a domain name in the

Q: How do I fix CVE-2013-4314?

pyopenssl: upgrade to newer than 0.13; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2013-4314 being exploited?

CVE-2013-4314 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2013-4314 affect?

CVE-2013-4314 affects pyopenssl, ubuntu linux. Severity is medium (CVSS 4.3). 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 v

Q: How urgent is CVE-2013-4314?

Priority 37/100. On your watchlist

Routine

MEDIUM 4.3WATCHLISTUPGRADEMITIGATE

CVE-2013-4314 is a medium-severity flaw (CVSS 4.3) affecting pyopenssl, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
EPSS exploit chance	1.2% (top 32%)
CISA exploited list	No
Weakness	CWE-20
Published	2013-09-30
Last modified	2026-06-16

Publisher (CNA): Red Hat, Inc. · Vendor: canonical · jean-paul calderone

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2013-09-30 21:55 UTCPublished CVE record published
2026-06-16 23:57 UTCUpdated Record last modified

jean-paul calderone pyopenssl UPGRADE

Affected: <= 0.13 · 0.7 · 0.8 a1 · 0.9 · 0.10 · 0.11 · 0.11 a1 · 0.11 a2

Fixed in: newer than 0.13

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy pyopenssl || rpm -q pyopenssl || pyopenssl --version

2. UPGRADE to newer than 0.13 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pyopenssl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pyopenssl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

canonical ubuntu linux MITIGATE

Affected: 10.04 · 12.04 · 12.10 · 13.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2013-4314?

pyopenssl: upgrade to newer than 0.13; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2013-4314 being exploited?

CVE-2013-4314 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2013-4314 affect?

CVE-2013-4314 affects pyopenssl, ubuntu linux. Severity is medium (CVSS 4.3). 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 v

How urgent is CVE-2013-4314?

Priority 37/100. On your watchlist

Software pages

Ubuntu vulnerabilities

Related CVEs

CVE-2026-27459 CRITICAL 9.8 UPGRADE pyOpenSSL is a Python wrapper around the OpenSSL library
CVE-2026-27448 MEDIUM 5.3 UPGRADE pyOpenSSL is a Python wrapper around the OpenSSL library
CVE-2018-1000808 MEDIUM 5.9 UPGRADE MITIGATE Python Cryptographic Authority pyopenssl version Before 17.5.0 contains a CWE - 401 : Failure to Release Memor
CVE-2018-1000807 HIGH 8.1 UPGRADE MITIGATE Python Cryptographic Authority pyopenssl version prior to version 17.5.0 contains a CWE-416: Use After Free vu

References

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