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             AUSCERT External Security Bulletin Redistribution

      MFSA 2021-50 Security Vulnerabilities fixed in Thunderbird 91.3
                              4 November 2021


        AusCERT Security Bulletin Summary

Product:           Thunderbird
Publisher:         Mozilla Foundation
Operating System:  UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Execute Arbitrary Code/Commands -- Remote with User Interaction
                   Denial of Service               -- Remote with User Interaction
                   Provide Misleading Information  -- Remote with User Interaction
                   Access Confidential Data        -- Remote with User Interaction
                   Reduced Security                -- Remote with User Interaction
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-38510 CVE-2021-38509 CVE-2021-38508
                   CVE-2021-38507 CVE-2021-38506 CVE-2021-38505
                   CVE-2021-38504 CVE-2021-38503 

Reference:         ESB-2021.3664

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

Mozilla Foundation Security Advisory 2021-50

Security Vulnerabilities fixed in Thunderbird 91.3

Announced: November  3, 2021
Impact:    high
Products:  Thunderbird
Fixed in:  Thunderbird 91.3

In general, these flaws cannot be exploited through email in the Thunderbird
product because scripting is disabled when reading mail, but are potentially
risks in browser or browser-like contexts.

# CVE-2021-38503: iframe sandbox rules did not apply to XSLT stylesheets

Reporter: Armin Ebert
Impact:   high


The iframe sandbox rules were not correctly applied to XSLT stylesheets,
allowing an iframe to bypass restrictions such as executing scripts or
navigating the top-level frame.


  o Bug 1729517

# CVE-2021-38504: Use-after-free in file picker dialog

Reporter: Irvan Kurniawan
Impact:   high


When interacting with an HTML input element's file picker dialog with
webkitdirectory set, a use-after-free could have resulted, leading to memory
corruption and a potentially exploitable crash.


  o Bug 1730156

# CVE-2021-38505: Windows 10 Cloud Clipboard may have recorded sensitive user

Reporter: Sergey Galich
Impact:   high


Microsoft introduced a new feature in Windows 10 known as Cloud Clipboard
which, if enabled, will record data copied to the clipboard to the cloud, and
make it available on other computers in certain scenarios. Applications that
wish to prevent copied data from being recorded in Cloud History must use
specific clipboard formats; and Thunderbird before version 91.3 did not
implement them. This could have caused sensitive data to be recorded to a
user's Microsoft account.
This bug only affects Thunderbird for Windows 10+ with Cloud Clipboard enabled.
Other operating systems are unaffected.


  o Bug 1730194

# CVE-2021-38506: Thunderbird could be coaxed into going into fullscreen mode
without notification or warning

Reporter: Irvan Kurniawan
Impact:   high


Through a series of web navigations, Thunderbird could have entered fullscreen
mode without notification or warning to the user. This could lead to spoofing
attacks on the browser UI including phishing.


  o Bug 1730750

# CVE-2021-38507: Opportunistic Encryption in HTTP2 could be used to bypass the
Same-Origin-Policy on services hosted on other ports

Reporter: Takeshi Terada
Impact:   high


The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to
be transparently upgraded to TLS while retaining the visual properties of an
HTTP connection, including being same-origin with unencrypted connections on
port 80. However, if a second encrypted port on the same IP address (e.g. port
8443) did not opt-in to opportunistic encryption; a network attacker could
forward a connection from the browser to port 443 to port 8443, causing the
browser to treat the content of port 8443 as same-origin with HTTP. This was
resolved by disabling the Opportunistic Encryption feature, which had low


  o Bug 1730935

#MOZ-2021-0008: Use-after-free in HTTP2 Session object

Reporter: Julien Cristau
Impact:   high


A use-after-free could have occured when an HTTP2 session object was released
on a different thread, leading to memory corruption and a potentially
exploitable crash.
Note: This issue is pending a CVE assignment and will be updated when


  o Bug 1667102

# CVE-2021-38508: Permission Prompt could be overlaid, resulting in user
confusion and potential spoofing

Reporter: Raphael
Impact:   moderate


By displaying a form validity message in the correct location at the same time
as a permission prompt (such as for geolocation), the validity message could
have obscured the prompt, resulting in the user potentially being tricked into
granting the permission.


  o Bug 1366818

# CVE-2021-38509: Javascript alert box could have been spoofed onto an arbitrary

Reporter: Ademar Nowasky Junior
Impact:   moderate


Due to an unusual sequence of attacker-controlled events, a Javascript alert()
dialog with arbitrary (although unstyled) contents could be displayed over top
an uncontrolled webpage of the attacker's choosing.


  o Bug 1718571

# CVE-2021-38510: Download Protections were bypassed by .inetloc files on Mac OS

Reporter: houjingyi647
Impact:   moderate


The executable file warning was not presented when downloading .inetloc files,
which, due to a flaw in Mac OS, can run commands on a user's computer.
Note: This issue only affected Mac OS operating systems. Other operating
systems are unaffected.


  o Bug 1731779

#MOZ-2021-0007: Memory safety bugs fixed in Thunderbird ESR 91.3

Reporter: Mozilla developers
Impact:   high


Mozilla developers and community members Christian Holler, Valentin Gosu, and
Andrew McCreight reported memory safety bugs present in Thunderbird 91.2. 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.
Note: This issue is pending a CVE assignment and will be updated when


  o Memory safety bugs fixed in Thunderbird 91.3

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