CVE-2021-43546: Security Vulnerabilities fixed in Firefox 95

Mozilla Foundation Security Advisory 2021-52

Announced

December 7, 2021

Impact

high

Products

Firefox

Fixed in

• Firefox 95

#CVE-2021-43536: URL leakage when navigating while executing asynchronous function

Reporter

Sunwoo Kim and Youngmin Kim of SNU CompSec Lab

Impact

high

Description

Under certain circumstances, asynchronous functions could have caused a navigation to fail but expose the target URL.

References

• Bug 1730120

#CVE-2021-43537: Heap buffer overflow when using structured clone

Reporter

bo13oy of Cyber Kunlun Lab

Impact

high

Description

An incorrect type conversion of sizes from 64bit to 32bit integers allowed an attacker to corrupt memory leading to a potentially exploitable crash.

References

• Bug 1738237

#CVE-2021-43538: Missing fullscreen and pointer lock notification when requesting both

Reporter

Irvan Kurniawan (@sourc7)

Impact

high

Description

By misusing a race in our notification code, an attacker could have forcefully hidden the notification for pages that had received full screen and pointer lock access, which could have been used for spoofing attacks.

References

• Bug 1739091

#CVE-2021-43539: GC rooting failure when calling wasm instance methods

Reporter

Asumu Takikawa and Ioanna Dimitriou

Impact

high

Description

Failure to correctly record the location of live pointers across wasm instance calls resulted in a GC occurring within the call not tracing those live pointers. This could have led to a use-after-free causing a potentially exploitable crash.

References

• Bug 1739683

#MOZ-2021-0010: Use-after-free in fullscreen objects on MacOS

Reporter

Atila Butkovits

Impact

high

Description

When transitioning in and out of fullscreen mode, a graphics object was not correctly protected; resulting in memory corruption and a potentially exploitable crash.
This bug only affects Firefox on MacOS. Other operating systems are unaffected.

References

• Bug 1735852

#CVE-2021-43540: WebExtensions could have installed persistent ServiceWorkers

Reporter

Jake Heath

Impact

moderate

Description

WebExtensions with the correct permissions were able to create and install ServiceWorkers for third-party websites that would not have been uninstalled with the extension.

References

• Bug 1636629

#CVE-2021-43541: External protocol handler parameters were unescaped

Reporter

chriscla

Impact

moderate

Description

When invoking protocol handlers for external protocols, a supplied parameter URL containing spaces was not properly escaped.

References

• Bug 1696685

#CVE-2021-43542: XMLHttpRequest error codes could have leaked the existence of an external protocol handler

Reporter

Raphael Smolik

Impact

moderate

Description

Using XMLHttpRequest, an attacker could have identified installed applications by probing error messages for loading external protocols.

References

• Bug 1723281

#CVE-2021-43543: Bypass of CSP sandbox directive when embedding

Reporter

Armin Ebert

Impact

moderate

Description

Documents loaded with the CSP sandbox directive could have escaped the sandbox’s script restriction by embedding additional content.

References

• Bug 1738418

#CVE-2021-43544: Receiving a malicious URL as text through a SEND intent could have led to XSS

Reporter

Irwan

Impact

moderate

Description

When receiving a URL through a SEND intent, Firefox would have searched for the text, but subsequent usages of the address bar might have caused the URL to load unintentionally, which could lead to XSS and spoofing attacks.
This bug only affects Firefox for Android. Other operating systems are unaffected.

References

• Bug 1739934

#CVE-2021-43545: Denial of Service when using the Location API in a loop

Reporter

Paul Zühlcke

Impact

low

Description

Using the Location API in a loop could have caused severe application hangs and crashes.

References

• Bug 1720926

#CVE-2021-43546: Cursor spoofing could overlay user interface when native cursor is zoomed

Reporter

Daniel Veditz

Impact

low

Description

It was possible to recreate previous cursor spoofing attacks against users with a zoomed native cursor.

References

• Bug 1737751

#MOZ-2021-0009: Memory safety bugs fixed in Firefox 95 and Firefox ESR 91.4

Reporter

Mozilla developers and community

Impact

high

Description

Mozilla developers and community members Julian Hector, Randell Jesup, Gabriele Svelto, Tyson Smith, Christian Holler, and Masayuki Nakano reported memory safety bugs present in Firefox 94. 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 Firefox 95