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AUSCERT External Security Bulletin Redistribution
MFSA 2021-54 Security Vulnerabilities fixed in Thunderbird 91.4.0
8 December 2021
AusCERT Security Bulletin Summary
Operating System: Windows
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Execute Arbitrary Code/Commands -- Remote with User Interaction
Cross-site Scripting -- 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
CVE Names: CVE-2021-43546 CVE-2021-43545 CVE-2021-43543
CVE-2021-43542 CVE-2021-43541 CVE-2021-43539
CVE-2021-43538 CVE-2021-43537 CVE-2021-43536
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Mozilla Foundation Security Advisory 2021-54
Security Vulnerabilities fixed in Thunderbird 91.4.0
Announced: December 7, 2021
Fixed in: Thunderbird 91.4
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-2021-43536: URL leakage when navigating while executing asynchronous
Reporter: Sunwoo Kim and Youngmin Kim of SNU CompSec Lab
Under certain circumstances, asynchronous functions could have caused a
navigation to fail but expose the target URL.
o Bug 1730120
# CVE-2021-43537: Heap buffer overflow when using structured clone
Reporter: bo13oy of Cyber Kunlun Lab
An incorrect type conversion of sizes from 64bit to 32bit integers allowed an
attacker to corrupt memory leading to a potentially exploitable crash.
o Bug 1738237
# CVE-2021-43538: Missing fullscreen and pointer lock notification when
Reporter: Irvan Kurniawan (@sourc7)
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.
o Bug 1739091
# CVE-2021-43539: GC rooting failure when calling wasm instance methods
Reporter: Asumu Takikawa and Ioanna Dimitriou
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
o Bug 1739683
# CVE-2021-43541: External protocol handler parameters were unescaped
When invoking protocol handlers for external protocols, a supplied parameter
URL containing spaces was not properly escaped.
o Bug 1696685
# CVE-2021-43542: XMLHttpRequest error codes could have leaked the existence of
an external protocol handler
Reporter: Raphael Smolik
Using XMLHttpRequest, an attacker could have identified installed applications
by probing error messages for loading external protocols.
o Bug 1723281
# CVE-2021-43543: Bypass of CSP sandbox directive when embedding
Reporter: Armin Ebert
Documents loaded with the CSP sandbox directive could have escaped the
sandbox's script restriction by embedding additional content.
o Bug 1738418
# CVE-2021-43545: Denial of Service when using the Location API in a loop
Reporter: Paul Zuhlcke
Using the Location API in a loop could have caused severe application hangs and
o Bug 1720926
# CVE-2021-43546: Cursor spoofing could overlay user interface when native
cursor is zoomed
Reporter: Daniel Veditz
It was possible to recreate previous cursor spoofing attacks against users with
a zoomed native cursor.
o Bug 1737751
Reporter: Pedro Batista
chrome-level privileges, but could be used as a stepping stone to further an
attack with other vulnerabilities.
o Bug 1742579
#MOZ-2021-0009: Memory safety bugs fixed in Thunderbird 91.4.0
Reporter: Mozilla developers and community
Mozilla developers and community members Julian Hector, Randell Jesup, Gabriele
Svelto, Tyson Smith, Christian Holler, and Masayuki Nakano reported memory
safety bugs present in Thunderbird 91.3. 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.
o Memory safety bugs fixed in Thunderbird 91.4.0
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