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CVE-2016-1839

Published: May 20, 2016Updated: May 6, 2026 Sources: CVE List NVD BDUCWE-125
5.5MEDIUM
NVD MITRE
EPSS Score
12.8%
Top 3.9%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

The xmlDictAddString function in libxml2 before 2.9.4, as used in Apple iOS before 9.3.2, OS X before 10.11.5, tvOS before 9.2.1, and watchOS before 2.2.1, allows remote attackers to cause a denial of service (heap-based buffer over-read) via a crafted XML document.

In plain language

AI Worth attention

This is a libxml2 XML-handling bug in older iPhones, Macs, Apple TVs, and Watches that can crash apps when they process a specially crafted XML document; most small businesses only need to worry if you handle XML from untrusted sources (like customer uploads, web gateways, or partner integrations).

Executive summary

CVE-2016-1839 is a libxml2 heap-based buffer over-read bug in xmlDictAddString (CWE-125) that can be triggered by remote attackers via a crafted XML document, leading to a denial of service; Apple fixed this in iOS 9.3.2, OS X 10.11.5, tvOS 9.2.1, and watchOS 2.2.1, and libxml2 was fixed in 2.9.4.

If affected, business impact
App/service crashes from XML inputInterruption to customer-facing workflowsPotential denial of service on gatewaysTime lost restoring availability

What to do now

  1. Check whether your business systems process XML from untrusted sources (web forms, customer uploads, APIs, emails, partner feeds), and identify which devices/services use the vulnerable libxml2 versions.
  2. If you run Apple devices/OS versions listed in the fix availability, upgrade to at least: iOS 9.3.2, OS X 10.11.5, tvOS 9.2.1, or watchOS 2.2.1.
  3. If you run Linux (including Ubuntu/Debian/Red Hat Enterprise Linux) or a “web gateway” that uses libxml2, upgrade libxml2 to 2.9.4 or newer.
  4. If you can’t upgrade immediately, reduce exposure by blocking untrusted XML sources at the entry point (only accept XML from trusted systems, and reject malformed/unexpected XML content).
Patch / advisory Usually a quick update

CVSS Vector Breakdown

AV:LAC:LPR:NUI:RS:UC:NI:NA:H
Exploitability
AV:LAttack Vector
Local
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-125

Affected Products

Apple Inc.
commercial·USaka apple, apple computer
iOSEmbeddedOS
Operating Systems / mobile-os
mac os xOn-premOS
Operating Systems / unix-bsd
tvosEmbeddedOS
Operating Systems / mobile-os
watchosEmbeddedOS
Operating Systems / mobile-os
OS X
Operating Systems
Canonical Ltd.
commercial·GBaka canonical
UbuntuOn-premOS
Operating Systems / linux-distro
debian
oss-project·GBaka debian gnu/linux
debian linuxOn-premOS
Operating Systems / linux-distro
Red Hat Inc.
commercial·USaka redhat, red hat
Red Hat Enterprise Linux ServerOn-premOS
Operating Systems / linux-distro
mcafee
commercial·USaka mcafee security, mcaee
web gateway
Security Products
xmlsoft
oss-projectaka libxml2, libxslt
libxml2LibraryLibrary
OSS Libraries / generic-library
and 12 more affected products View all →

Exploitability

Official Patch Available
Is your org exposed to CVE-2016-1839?We can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Collection
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References

http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html
oracle.com
https://kc.mcafee.com/corporate/index?page=content&id=SB10170
kc.mcafee.com
https://access.redhat.com/errata/RHSA-2016:1292
access.redhat.com
and 34 more references View all →

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