CVE-2016-4658
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.
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.
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert: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 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | 9.8 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | High | N/A |
| Integrity Impact | None | High | N/A |
| Availability Impact | None | High | N/A |
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.
CVSS v2 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | 10 | N/A |
| Attack Vector | Network | Network | N/A |
| Access Complexity | Medium | Low | N/A |
| Authentication | None | None | N/A |
| Confidentiality Impact | Partial | Complete | N/A |
| Integrity Impact | None | Complete | N/A |
| Availability Impact | None | Complete | N/A |
Vector
Red Hat: AV:N/AC:M/Au:N/C:P/I:N/A:N
NVD: AV:N/AC:L/Au:N/C:C/I:C/A:C
Understanding the Weakness (CWE)
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.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
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.
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