CyberSecBulletin
CVE-2019-0541Exploited in the wildNVD status: Analyzed

Microsoft MSHTML Remote Code Execution

Published Updated By the CyberSecBulletin desk

CVE-2019-0541 is a high-severity improper neutralization of special elements used in a command vulnerability in Microsoft Office from Microsoft, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected Microsoft Office versions: 2010 Service Pack 2 (32-bit editions); 2010 Service Pack 2 (64-bit editions); 2013 RT Service Pack 1, and others listed below. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Check which version of Microsoft Office you run against the affected versions below, and install the vendor's latest release.
  2. CISA's required action: Apply updates per vendor instructions.
  3. Read the advisory on portal.msrc.microsoft.com for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  5. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftMicrosoft Office2010 Service Pack 2 (32-bit editions); 2010 Service Pack 2 (64-bit editions); 2013 RT Service Pack 1; 2013 Service Pack 1 (32-bit editions); 2013 Service Pack 1 (64-bit editions); 2016 (32-bit edition); 2016 (64-bit edition); 2019 for 32-bit editions; and 1 more rangesNot stated
MicrosoftMicrosoft Office Word ViewerMicrosoft Office Word ViewerNot stated
MicrosoftInternet Explorer 9Windows Server 2008 for 32-bit Systems Service Pack 2; Windows Server 2008 for x64-based Systems Service Pack 2Not stated
MicrosoftInternet Explorer 11Windows 10 for 32-bit Systems; Windows 10 for x64-based Systems; Windows 10 Version 1607 for 32-bit Systems; Windows 10 Version 1607 for x64-based Systems; Windows 10 Version 1703 for 32-bit Systems; Windows 10 Version 1703 for x64-based Systems; Windows 10 Version 1709 for 32-bit Systems; Windows 10 Version 1709 for ARM64-based Systems; and 16 more rangesNot stated
MicrosoftMicrosoft Excel Viewer2007 Service Pack 3Not stated
MicrosoftInternet Explorer 10Windows Server 2012Not stated
MicrosoftOffice365 ProPlus for 32-bit Systems; 365 ProPlus for 64-bit SystemsNot stated
MicrosoftInternet Explorer11; 9; 10Not stated
MicrosoftExcel Viewer2007Not stated
MicrosoftOffice 365 ProplusNot specified in the recordNot stated
MicrosoftOffice Word ViewerNot specified in the recordNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.18.8HighNVD
CVSS 3.18.8HighCISA (ADP)
CVSS 2.09.3HighNVD

Official description

A remote code execution vulnerability exists in the way that the MSHTML engine inproperly validates input, aka "MSHTML Engine Remote Code Execution Vulnerability." This affects Microsoft Office, Microsoft Office Word Viewer, Internet Explorer 9, Internet Explorer 11, Microsoft Excel Viewer, Internet Explorer 10, Office 365 ProPlus.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements used in a Command

The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

How developers prevent this class of flaw

  • If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • If possible, ensure that all external commands called from the program are statically created.
  • Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.

More Improper Neutralization of Special Elements used in a Command vulnerabilities (CWE-77)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. Deadline for US federal agencies to remediate, set by CISA.
  4. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Technical write-ups (may include proof of concept)

Other vulnerabilities in Microsoft Office

All Microsoft Office vulnerabilities

Recent Improper Neutralization of Special Elements used in a Command vulnerabilities

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