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Libxml2 CVE-2016-4449

HIGH
Improper Input Validation (CWE-20)
2016-06-09 secalert@redhat.com
Denial Of Service XXE Debian Canonical Debian Linux Libxml2 Ubuntu Linux Xmlsoft
7.1
CVSS 3.0 · NVD
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Vulnerability Assessment

Weakness
CWE
CWE-20
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V2 - Validation and Business Logic Input validation, allowlisting
Impact

CVSS score of 7.1 (HIGH). Attack characteristics: local attack vector, low complexity, no privileges required, user interaction required. EPSS exploitation probability: 0.12%.
Exploit ScenarioDerived

Successful exploitation could compromise the high-severity affected system.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.1% exploitation probability (EPSS)

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AnalysisAI

XML external entity (XXE) vulnerability in the xmlStringLenDecodeEntities function in parser.c in libxml2 before 2.9.4, when not in validating mode, allows context-dependent attackers to read. Rated high severity (CVSS 7.1), this vulnerability is no authentication required, low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

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Technical ContextAI · show details

This vulnerability is classified under CWE-20. XML external entity (XXE) vulnerability in the xmlStringLenDecodeEntities function in parser.c in libxml2 before 2.9.4, when not in validating mode, allows context-dependent attackers to read arbitrary files or cause a denial of service (resource consumption) via unspecified vectors. Affected products include: Debian Debian Linux, Canonical Ubuntu Linux, Xmlsoft Libxml2. Version information: before 2.9.4.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

NVD PRIMARY 7.1 HIGH
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

DescriptionCVE.org

XML external entity (XXE) vulnerability in the xmlStringLenDecodeEntities function in parser.c in libxml2 before 2.9.4, when not in validating mode, allows context-dependent attackers to read arbitrary files or cause a denial of service (resource consumption) via unspecified vectors.

Threat Intelligence Overview

EPSS Score
0.1%
Top 69% exploitable
Data Quality
3 sources
Confidence: Low
NVD CVE.org EPSS

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 HIGH
CISA KEV No
Public POC No
EPSS 0.1%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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
Defer
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

36
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +36
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

XML External Entity Injection HIGH

XML External Entity (XXE) attacks exploit XML parsers that process Document Type Definitions (DTDs) without proper restrictions.

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)CVE.org

cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:12.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:15.10:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
cpe:2.3:a:xmlsoft:libxml2:*:*:*:*:*:*:*:*

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Same weakness CWE-20 – Improper Input Validation

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Same technique Denial Of Service

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References

Advisories & patches
ADVISORY https://git.gnome.org/browse/libxml2/commit/?id=b1d34de46a11323fccffa9fadeb33be670d602f5 REF http://jvn.jp/en/jp/JVN17535578/index.html REF http://jvndb.jvn.jp/en/contents/2017/JVNDB-2017-000066.html REF http://lists.apple.com/archives/security-announce/2016/Jul/msg00000.html REF http://lists.apple.com/archives/security-announce/2016/Jul/msg00001.html REF http://lists.apple.com/archives/security-announce/2016/Jul/msg00002.html REF http://lists.apple.com/archives/security-announce/2016/Jul/msg00003.html REF http://lists.apple.com/archives/security-announce/2016/Jul/msg00005.html REF http://rhn.redhat.com/errata/RHSA-2016-2957.html REF http://www.openwall.com/lists/oss-security/2016/05/25/2 REF http://www.oracle.com/technetwork/security-advisory/cpujan2018-3236628.html REF http://www.oracle.com/technetwork/topics/security/bulletinjul2016-3090568.html REF http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html REF http://www.securityfocus.com/bid/90865 REF http://www.securitytracker.com/id/1036348 REF http://www.slackware.com/security/viewer.php?l=slackware-security&y=2016&m=slackware-security.404722 REF http://www.ubuntu.com/usn/USN-2994-1 REF http://xmlsoft.org/news.html REF https://access.redhat.com/errata/RHSA-2016:1292 REF https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05194709 REF https://kc.mcafee.com/corporate/index?page=content&id=SB10170 REF https://support.apple.com/HT206899 REF https://support.apple.com/HT206901 REF https://support.apple.com/HT206902 REF https://support.apple.com/HT206903 REF https://support.apple.com/HT206904 REF https://support.apple.com/HT206905 REF https://support.cybozu.com/ja-jp/article/9735 REF https://www.debian.org/security/2016/dsa-3593 REF https://www.tenable.com/security/tns-2016-18

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