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Pyopenssl CVE-2013-4314

MEDIUM
Improper Input Validation (CWE-20)
2013-09-30 secalert@redhat.com
4.3
CVSS 2.0 · NVD
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V2 - Validation and Business Logic Input validation, allowlisting
Impact

CVSS score of 4.3 (MEDIUM). Attack characteristics: network attack vector, M complexity. EPSS exploitation probability: 0.25%.

Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the medium-severity affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAI

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. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affected Packages

pypi pyopenssl fix: 0.13.1

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in pypi

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-20. 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. Affected products include: Jean-Paul Calderone Pyopenssl, Canonical Ubuntu Linux. Version information: before 0.13.1.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 4.3 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
M
Confidentiality
None
Integrity
P
Availability
None

DescriptionCVE.org

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.

Threat Intelligence Overview

EPSS Score
0.2%
Top 52% exploitable
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

22
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +22
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)CVE.org

cpe:2.3:a:jean-paul_calderone:pyopenssl:*:*:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.7:*:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.8:a1:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.9:*:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.10:*:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.11:*:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.11:a1:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.11:a2:*:*:*:*:*:*
cpe:2.3:a:jean-paul_calderone:pyopenssl:0.12:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:10.04:-:lts:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:12.04:-:lts:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:12.10:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:13.04:*:*:*:*:*:*:*

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