CVE-2013-4238

What it is

The ssl.match_hostname function in the SSL module in Python 2.6 through 3.4 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, a related issue to CVE-2009-2408.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

5.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2013-08-18 02:52 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-16 23:56 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 5.3% in the next 30 days (EPSS).
• Severity: 4.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2013-08-18 02:52 UTC

Last modified

2026-06-16 23:56 UTC

Exploit probability

5.3% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Modified

Affected

• Canonical Ubuntu Linux 10.04
• Python 2.6.1
• Python 2.6.2
• Python 2.6.3
• Python 2.6.4
• Python 2.6.5
• Python 2.6.6
• Python 2.6.7

Attack profile CVSS 2.0 · 4.3

Attack vector

Network

Complexity

Medium

Authentication

None

Confidentiality

None

Integrity

Partial

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2013-4238.md and follow it. Check whether this project is affected by CVE-2013-4238. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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