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McAfee Security Bulletin: McAfee Web Gateway update fixes several vulnerabilities related to xml parsing
Security Bulletins ID:   SB10170
Last Modified:  4/7/2017

Summary

First Published: October 5, 2016
 
 Impact of Vulnerability: Buffer Overflow (CWE-726, OWASP 2004:A5)
Code Injection (CWE-94)
Denial of Service (CWE-730, OWASP 2004:A9)
Input Validation (CWE-20)
Resource Management Error (CWE-399)
Out-of-bounds Read (CWE-125)
Use After Free (CWE-416)
 CVE Numbers: CVE-2016-1762
CVE-2016-1833
CVE-2016-1834
CVE-2016-1835
CVE-2016-1836
CVE-2016-1837
CVE-2016-1838
CVE-2016-1839
CVE-2016-1840
CVE-2016-3627
CVE-2016-3705
CVE-2016-4447
CVE-2016-4448
CVE-2016-4449
 Severity Rating: Medium, Low
 Base / Overall CVSS v3 Scores: CVE-2016-1762 – Base: 4.3 Temp: 3.8
CVE-2016-1833 – Base: 4.3 Temp: 3.8
CVE-2016-1834 – Base: 5.4 Temp: 4.7
CVE-2016-1835 – Base: 4.3 Temp: 3.8
CVE-2016-1836 – Base: 4.3 Temp: 3.8
CVE-2016-1837 – Base: 4.3 Temp: 3.8
CVE-2016-1838 – Base: 4.3 Temp: 3.8
CVE-2016-1839 – Base: 4.3 Temp: 3.8
CVE-2016-1840 – Base: 4.2 Temp: 3.7
CVE-2016-3627 – Base: 4.3 Temp: 3.8
CVE-2016-3705 – Base: 4.3 Temp: 3.8
CVE-2016-4447 – Base: 4.3 Temp: 3.8
CVE-2016-4448 – Base: 4.2 Temp: 3.7
CVE-2016-4449 – Base: 5.4 Temp: 4.7
 Recommendations: Update to latest McAfee Web Gateway (MWG) releases: 7.7.0, 7.6.2.4, or 7.5.2.11.
 Security Bulletin Replacement: None
 Affected Software: MWG 7.6.2.3 and earlier; MWG 7.5.2.10 and earlier
 Location of Updated Software:  https://contentsecurity.mcafee.com/software_mwg7_download
 
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Article contents:

Description

libxml2 contains several vulnerabilities. MWG consumes libxml2 for parsing xml documents that are part of the web traffic and thereby it inherits the vulnerabilities.

CVE-2016-1762
The xmlNextChar function in libxml2 before 2.9.4 allows remote attackers to cause a denial of service (heap-based buffer over-read) via a crafted XML document. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1762

CVE-2016-1833
The htmlCurrentChar 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. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1833

CVE-2016-1834
Heap-based buffer overflow in the xmlStrncat 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 execute arbitrary code or cause a denial of service (memory corruption) via a crafted XML document.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1834

CVE-2016-1835
Use-after-free vulnerability in the xmlSAX2AttributeNs function in libxml2 before 2.9.4, as used in Apple iOS before 9.3.2 and OS X before 10.11.5, allows remote attackers to cause a denial of service via a crafted XML document.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1835

CVE-2016-1836
Use-after-free vulnerability in the xmlDictComputeFastKey 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 via a crafted XML document.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1836

CVE-2016-1837
Multiple use-after-free vulnerabilities in the (1) htmlPArsePubidLiteral and (2) htmlParseSystemiteral functions 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, allow remote attackers to cause a denial of service via a crafted XML document.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1837

CVE-2016-1838
The xmlPArserPrintFileContextInternal 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.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1838

CVE-2016-1839
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.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1839

CVE-2016-1840
Heap-based buffer overflow in the xmlFAParsePosCharGroup 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 execute arbitrary code or cause a denial of service (memory corruption) via a crafted XML document
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-1840

CVE-2016-3627
Missing recursive loop detection checks were found in the xmlParserEntityCheck() and xmlStringGetNodeList() functions of libxml2, causing application using the library to crash by stack exhaustion while building the associated data. An attacker able to send XML data to be parsed in recovery mode could launch a Denial of Service on the application.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-3627

CVE-2016-3705
Missing incrementation of recursion depth counter were found in the xmlParserEntityCheck() and xmlParseAttValueComplex() functions used for parsing XML data. An attacker could launch a Denial of Service attack by passing specially crafted XML data to an application, forcing it to crash due to stack exhaustion.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-3705

CVE-2016-4447
The xmlParseElementDecl function in parser.c in libxml2 before 2.9.4 allows context-dependent attackers to cause a denial of service (heap-based buffer underread and application crash) via a crafted file, involving xmlParseName.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-4447

CVE-2016-4448
Format string vulnerability in libxml2 before 2.9.4 allows attackers to have unspecified impact via format string specifiers in unknown vectors.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-4448

CVE-2016-4449
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.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-4449


CWE-726: Buffer Overflow http://cwe.mitre.org/data/definitions/726.html
CWE-94: Code Injection http://cwe.mitre.org/data/definitions/94.html
CWE-730: Denial of Service http://cwe.mitre.org/data/definitions/730.html
CWE-20: Input Validation http://cwe.mitre.org/data/definitions/20.html
CWE-399: Resource Management Error http://cwe.mitre.org/data/definitions/399.html
CWE-125: Out-of-bounds Read http://cwe.mitre.org/data/definitions/125.html 
CWE-416: Use After Free https://cwe.mitre.org/data/definitions/416.html

This flaw is encountered if MWG opens an xml file that was specifically crafted by an attacker.

Remediation

Install the latest version.

Go to the Product Downloads site and download the applicable product patch/hotfix files:
 
Product Type Version File Name Release Date
MWG 7.6.2.4 Maintenance Release 7.6.2.4 n/a September 28, 2016
MWG 7.5.2.11 Maintenance Release 7.5.2.11 n/a September 28, 2016

Download and Installation Instructions
See release notes that come with the new MWG release for further instructions at: https://contentsecurity.mcafee.com/software_mwg7_download

Workaround

Disable opening of xml files. In other words, add criteria to the rule that enables the openers, so that it checks the media type of the body and only executes the rule if it is not xml. Work with Technical Support if you need further help on this.

McAfee strongly recommends you install the available version updates. If you cannot, consider the instructions above as a temporary workaround.

Mitigations

No vulnerability detection signatures are available.
 

Acknowledgements

This vulnerability was first disclosed by The MITRE Corporation (http://cve.mitre.org/) as a CVE.
 

Support

Corporate Technical Support: 
1-800-338-8754
http://www.mcafee.com/us/about/contact-us.aspx#ht=tab-techsupport 
 

Frequently Asked Questions (FAQs)

How do I know whether my McAfee product is vulnerable or not?

For Endpoint products:
Use the following instructions for endpoint or client based products:
  1. Right-click on the McAfee tray shield icon on the Windows task bar.
  2. Select Open Console.
  3. In the console, select Action Menu.
  4. In the Action Menu, select Product Details. The product version is displayed.
For ePO:
Check the version and build of ePO that is installed. For information on how to check the version, see KB52634.

For Appliances:
Use the following instructions for Appliance based products:
  1. Open the Administrator's User Interface (UI).
  2. Click the About link. The product version is displayed.
For DLPe ePO Extension:
Use the following instructions:
  1. Log on to ePO server.
  2. Click Menu, Data Protection, DLP Policy.
  3. Inside the DLP console click the Help menu item, About. The product version is displayed.
For McAfee Firewall Enterprise:
Use the following instructions:
  1. In the Admin Console, select Maintenance, Software Management.
  2. The base product version and installed patches are displayed.
What is CVSS?
CVSS, or Common Vulnerability Scoring System, is the result of the National Infrastructure Advisory Council’s effort to standardize a system of assessing the criticality of a vulnerability. This system offers an unbiased criticality score between 0 and 10 that customers can use to judge how critical a vulnerability is and plan accordingly. For more information, please visit the CVSS website at: http://www.first.org/cvss/.

When calculating CVSS scores, McAfee has adopted a philosophy that fosters consistency and repeatability. Our guiding principle for CVSS scoring is to score the exploit under consideration by itself. We consider only the immediate and direct impact of the exploit under consideration. We do not factor into a score any potential follow-on exploits that might be made possible by successful exploitation of the issue being scored
 
What are the CVSS scoring metrics that have been used?
 
CVE-2016-1834
 
Base Score
5.3
Attack Vector (AV)
Network (N)
Attack Complexity (AC)
Low (L)
Privileges Required (PR)
None (N)
User Interaction (UI)
Required (R)
Scope (S)
Unchanged (U)
Confidentiality (C)
Low (L)
Integrity (I)
None (N)
Availability (A)
Low (L)
Temporal Score (Overall)
4.7
Exploitability (E)
Unproven (U)
Remediation Level (RL)
Official Fix (O)
Report Confidence (RC)
Confirmed (C)
 
NOTE: The below CVSS version 3.0 vector was used to generate this score. https://nvd.nist.gov/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L/E:U/RL:O/RC:C
 
 
CVE-2016-1762
CVE-2016-1833
CVE-2016-1835
CVE-2016-1836
CVE-2016-1837
CVE-2016-1838
CVE-2016-1839
CVE-2016-3627
CVE-2016-3705
CVE-2016-4447
 
Base Score
4.3
Attack Vector (AV)
Network (N)
Attack Complexity (AC)
Low (L)
Privileges Required (PR)
None (N)
User Interaction (UI)
Required (R)
Scope (S)
Unchanged (U)
Confidentiality (C)
None (N)
Integrity (I)
None (N)
Availability (A)
Low (L)
Temporal Score (Overall)
3.8
Exploitability (E)
Unproven (U)
Remediation Level (RL)
Official Fix (O)
Report Confidence (RC)
Confirmed (C)
 
NOTE: The below CVSS version 3.0 vector was used to generate this score. https://nvd.nist.gov/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C
 
 
CVE-2016-1840
CVE-2016-4448
 
Base Score
4.2
Attack Vector (AV)
Network (N)
Attack Complexity (AC)
High (H)
Privileges Required (PR)
None (N)
User Interaction (UI)
Required (R)
Scope (S)
Unchanged (U)
Confidentiality (C)
Low (L)
Integrity (I)
None (N)
Availability (A)
Low (L)
Temporal Score (Overall)
3.7
Exploitability (E)
Unproven (U)
Remediation Level (RL)
Official Fix (O)
Report Confidence (RC)
Confirmed (C)
 
NOTE: The below CVSS version 3.0 vector was used to generate this score. https://nvd.nist.gov/cvss/v3-calculator?vector=AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L/E:U/RL:O/RC:C
 
 
CVE-2016-4449
 
Base Score
5.4
Attack Vector (AV)
Network (N)
Attack Complexity (AC)
Low (L)
Privileges Required (PR)
None (N)
User Interaction (UI)
Required (R)
Scope (S)
Unchanged (U)
Confidentiality (C)
Low (L)
Integrity (I)
None (N)
Availability (A)
Low (L)
Temporal Score (Overall)
4.7
Exploitability (E)
Unproven (U)
Remediation Level (RL)
Official Fix (O)
Report Confidence (RC)
Confirmed (C)
 
NOTE: The below CVSS version 3.0 vector was used to generate this score. https://nvd.nist.gov/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L/E:U/RL:O/RC:C

 

Where can I find a list of all security bulletins or how do I report a product vulnerability?
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