Rewterz Threat Advisory – Mozilla Releases Security Updates for Multiple Products

Wednesday, February 12, 2020



Analysis Summary

Mozilla has released security updates to address vulnerabilities in Firefox, Firefox ESR, and Thunderbird. An attacker could exploit some of these vulnerabilities to take control of an affected system.

CVE-2020-6792: Message ID calculcation was based on uninitialized data

When deriving an identifier for an email message, uninitialized memory was used in addition to the message contents.

CVE-2020-6793: Out-of-bounds read when processing certain email messages

When processing an email message with an ill-formed envelope, Thunderbird could read data from a random memory location.

CVE-2020-6794: Setting a master password post-Thunderbird 52 does not delete unencrypted previously stored passwords

If a user saved passwords before Thunderbird 60 and then later set a master password, an unencrypted copy of these passwords is still accessible. This is because the older stored password file was not deleted when the data was copied to a new format starting in Thunderbird 60. The new master password is added only on the new file. This could allow the exposure of stored password data outside of user expectations.

CVE-2020-6795: Crash processing S/MIME messages with multiple signatures

When processing a message that contains multiple S/MIME signatures, a bug in the MIME processing code caused a null pointer dereference, leading to an unexploitable crash.

CVE-2020-6796: Missing bounds check on shared memory read in the parent process

A content process could have modified shared memory relating to crash reporting information, crash itself, and cause an out-of-bound write. This could have caused memory corruption and a potentially exploitable crash.

CVE-2020-6797: Extensions granted permission could open arbitrary applications on Mac OSX

By downloading a file with the .fileloc extension, a semi-privileged extension could launch an arbitrary application on the user’s computer. The attacker is restricted as they are unable to download non-quarantined files or supply command line arguments to the application, limiting the impact.

CVE-2020-6798: Incorrect parsing of template tag could result in JavaScript injection

If a <template> tag was used in a <select%gt; tag, the parser could be confused and allow JavaScript parsing and execution when it should not be allowed. A site that relied on the browser behaving correctly could suffer a cross-site scripting vulnerability as a result. 

CVE-2020-6799: Arbitrary code execution when opening pdf links from other applications, when Firefox is configured as default pdf reader

Command line arguments could have been injected during Firefox invocation as a shell handler for certain unsupported file types. This required Firefox to be configured as the default handler for a given file type and for a file downloaded to be opened in a third party application that insufficiently sanitized URL data. In that situation, clicking a link in the third party application could have been used to retrieve and execute files whose location was supplied through command line arguments.

CVE-2020-6800: Memory safety bugs fixed in Firefox 73 and Firefox ESR 68.5

Mozilla developers and community members Raul Gurzau, Tyson Smith, Bob Clary, Liz Henry, and Christian Holler reported memory safety bugs present in Firefox 72 and Firefox ESR 68.4. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.

CVE-2020-6801: Memory safety bugs fixed in Firefox 73

Mozilla developers Jason Kratzer, Tyson Smith, and Christian Holler reported memory safety bugs present in Firefox 72. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.


  • System Takeover
  • Password Exposure
  • Denial of Service
  • Memory Corruption
  • Cross-site Scripting
  • Execution of arbitrary code

Affected Vendors


Affected Products

  • Mozilla Firefox ESR
  • Mozilla Firefox
  • Thunderbird


Update these products to the following fixed versions.

  • Firefox 73
  • Thunderbird 68.5
  • Firefox ESR68.5

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