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Multiple Vulnerabilities in Mozilla Thunderbird Could Allow for Arbitrary Code Execution

MS-ISAC ADVISORY NUMBER:

2018-058

DATE(S) ISSUED:

05/21/2018

OVERVIEW:

Multiple vulnerabilities have been discovered in Mozilla Thunderbird, the most severe of which could allow for arbitrary code execution. Mozilla Thunderbird is an email client. Successful exploitation of the most severe of these vulnerabilities could allow for arbitrary code execution. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

THREAT INTELLIGENCE:

There are currently no reports of these vulnerabilities being exploited in the wild.

SYSTEMS AFFECTED:

  • Mozilla Thunderbird versions prior to 52.8

RISK:

Government:
  • Large and medium government entities: HIGH
  • Small government entities: MEDIUM
Businesses:
  • Large and medium business entities: HIGH
  • Small business entities: MEDIUM
Home Users:
LOW

TECHNICAL SUMMARY:

Multiple vulnerabilities have been identified in Mozilla Thunderbird, the most severe of which could allow for arbitrary code execution. Mozilla Thunderbird version 52.8 includes the fixes for PGP & S/MIME “EFAIL” vulnerability. Details of the vulnerabilities are as follows:

  • Multiple memory corruption vulnerabilities which could result in arbitrary code execution. (CVE-2018-5150)
  • A use-after-free vulnerability can occur while enumerating attributes during SVG animations with clip paths. This results in a potentially exploitable crash. (CVE-2018-5154)
  • A use-after-free vulnerability can occur while adjusting layout during SVG animations with text paths. This results in a potentially exploitable crash. (CVE-2018-5155)
  • An integer overflow can occur in the Skia library due to 32-bit integer use in an array without integer overflow checks, resulting in possible out-of-bounds writes. This could lead to a potentially exploitable crash triggerable by web content. (CVE-2018-5159)
  • Crafted message headers can cause a Thunderbird process to hang on receiving the message. (CVE-2018-5161)
  • Plaintext of decrypted emails can leak through the src attribute of remote images, or links. (CVE-2018-5162)
  • Sites can bypass security checks on permissions to install lightweight themes by manipulating the baseURI property of the theme element. This could allow a malicious site to install a theme without user interaction which could contain offensive or embarrassing images. (CVE-2018-5168)
  • It is possible to spoof the filename of an attachment and display an arbitrary attachment name. This could lead to a user opening a remote attachment which is a different file type than expected. (CVE-2018-5170)
  • In the Windows 10 April 2018 Update, Windows Defender SmartScreen honors the SEE_MASK_FLAG_NO_UI flag associated with downloaded files and will not show any UI. Files that are unknown and potentially dangerous will be allowed to run because SmartScreen will not prompt the user for a decision, and if the user is offline all files will be allowed to be opened because Windows won’t prompt the user to ask what to do. Firefox incorrectly sets this flag when downloading files, leading to less secure behavior from SmartScreen. Note: this issue only affects Windows 10 users running the April 2018 update or later. It does not affect other Windows users or other operating systems. (CVE-2018-5174)
  • A buffer overflow was found during UTF8 to Unicode string conversion within JavaScript with extremely large amounts of data. This vulnerability requires the use of a malicious or vulnerable legacy extension in order to occur. (CVE-2018-5178)
  • Mozilla developers backported selected changes in the Skia library. These changes correct memory corruption issues including invalid buffer reads and writes during graphic operations. (CVE-2018-5183)
  • Using remote content in encrypted messages can lead to the disclosure of plaintext. (CVE-2018-5184)
  • Plaintext of decrypted emails can leak through by user submitting an embedded form. (CVE-2018-5185)

Successful exploitation of the most severe of these vulnerabilities could allow for arbitrary code execution. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

RECOMENDATIONS:

We recommend the following actions be taken:

  • Apply appropriate updates provided by Mozilla to vulnerable systems, immediately after appropriate testing.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
  • Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
  • Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources.
  • Apply the Principle of Least Privilege to all systems and services.

REFERENCES:

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