CVE-2021-43535: Security Vulnerabilities fixed in Thunderbird 91.3

Mozilla Foundation Security Advisory 2021-50

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

Description

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.

References

• Bug 1729517

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

Reporter

Irvan Kurniawan

Impact

high

Description

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.

References

• Bug 1730156

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

Reporter

Sergey Galich

Impact

high

Description

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.

References

• Bug 1730194

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

Reporter

Irvan Kurniawan

Impact

high

Description

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.

References

• 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

Description

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 usage.

References

• Bug 1730935

#CVE-2021-43535: Use-after-free in HTTP2 Session object

Reporter

Julien Cristau

Impact

high

Description

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.

References

• Bug 1667102

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

Reporter

Raphael

Impact

moderate

Description

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.

References

• Bug 1366818

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

Reporter

Ademar Nowasky Junior

Impact

moderate

Description

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.

References

• Bug 1718571

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

Reporter

Hou JingYi

Impact

moderate

Description

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.

References

• Bug 1731779

#CVE-2021-43534: Memory safety bugs fixed in Thunderbird ESR 91.3

Reporter

Mozilla developers

Impact

high

Description

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.

References

• Memory safety bugs fixed in Thunderbird 91.3