CVE-2016-4658

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ModerateModerate ImpactWhat does this mean?
DescriptionStatementMitigationAdditional informationCVSS Score DetailsWeakness (CWE)FAQ

Description

A use-after-free flaw was found in the Xpointer implementation of libxml2. An attacker could use this flaw against an application parsing untrusted XML files and compiled with libxml2 to leak small amount of memory data.

A use-after-free flaw was found in the Xpointer implementation of libxml2. An attacker could use this flaw against an application parsing untrusted XML files and compiled with libxml2 to leak small amount of memory data.

Statement

This flaw can be triggered by parsing untrusted XML files via applications compiled with libxml2 causing the application to crash. For web browsers or browser like applications, which parse untrusted web content, it may be possible to trigger this flaw without any user intervention and cause remote code execution with the permissions of the user running the browser. For other applications this flaw is difficult to trigger and even difficult to exploit in real life situations. The status of mingw-libxml2 package in RHEL-8 is marked as "not-affected" because it does not impact end-users.

This flaw can be triggered by parsing untrusted XML files via applications compiled with libxml2 causing the application to crash. For web browsers or browser like applications, which parse untrusted web content, it may be possible to trigger this flaw without any user intervention and cause remote code execution with the permissions of the user running the browser. For other applications this flaw is difficult to trigger and even difficult to exploit in real life situations.

The status of mingw-libxml2 package in RHEL-8 is marked as "not-affected" because it does not impact end-users.

Mitigation

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Additional information

  • Bugzilla 1384424: libxml2: Use after free via namespace node in XPointer ranges
  • CWE-416: Use After Free
  • FAQ: Frequently asked questions about CVE-2016-4658

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).

CVSS v3
CVSS v3 Score Breakdown
Red HatNVD

CVSS v3 Base Score

5.3

9.8

Attack Vector

Network

Network

Attack Complexity

Low

Low

Privileges Required

None

None

User Interaction

None

None

Scope

Unchanged

Unchanged

Confidentiality Impact

Low

High

Integrity Impact

None

High

Availability Impact

None

High

CVSS v3 Vector

Red Hat: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

NVD: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Red Hat CVSS v3 Score Explanation

Exploitation of this flaw in libxml2 versions shipped by Red Hat is only able to indirectly disclose small amounts of heap memory contents (C:L), no integrity or availability impact is possible (I:N/A:N). NVD rating assumes the worst-case of a use-after-free flaw (C:H/I:H/A:H) which may be possible on versions we have not analysed.

Exploitation of this flaw in libxml2 versions shipped by Red Hat is only able to indirectly disclose small amounts of heap memory contents (C:L), no integrity or availability impact is possible (I:N/A:N). NVD rating assumes the worst-case of a use-after-free flaw (C:H/I:H/A:H) which may be possible on versions we have not analysed.

CVSS v2

Understanding the Weakness (CWE)

CWE-416

Integrity

Technical Impact: Modify Memory

The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.

Availability

Technical Impact: DoS: Crash, Exit, or Restart

If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.

Integrity,Confidentiality,Availability

Technical Impact: Execute Unauthorized Code or Commands

If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?

What can I do if my product is listed as "Will not fix"?

What can I do if my product is listed as "Fix deferred"?

What is a mitigation?

I have a Red Hat product but it is not in the above list, is it affected?

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

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