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AUSCERT External Security Bulletin Redistribution
MFSA 2020-29 Security Vulnerabilities fixed in Thunderbird 78
17 July 2020
AusCERT Security Bulletin Summary
Operating System: Windows
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Execute Arbitrary Code/Commands -- Remote with User Interaction
Denial of Service -- Remote with User Interaction
Access Confidential Data -- Remote with User Interaction
Unauthorised Access -- Remote with User Interaction
Reduced Security -- Remote with User Interaction
CVE Names: CVE-2020-15648 CVE-2020-12426 CVE-2020-12425
CVE-2020-12424 CVE-2020-12423 CVE-2020-12422
CVE-2020-12421 CVE-2020-12420 CVE-2020-12419
CVE-2020-12418 CVE-2020-12417 CVE-2020-12416
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Mozilla Foundation Security Advisory 2020-29
Security Vulnerabilities fixed in Thunderbird 78
July 16, 2020
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-2020-12415: AppCache manifest poisoning due to url encoded character
When %2F was present in a manifest URL, Thunderbird's AppCache behavior may
have become confused and allowed a manifest to be served from a subdirectory.
This could cause the appcache to be used to service requests for the top level
o Bug 1586630
# CVE-2020-12416: Use-after-free in WebRTC VideoBroadcaster
A VideoStreamEncoder may have been freed in a race condition with
VideoBroadcaster::AddOrUpdateSink , resulting in a use-after-free, memory
corruption, and a potentially exploitable crash.
o Bug 1639734
# CVE-2020-12417: Memory corruption due to missing sign-extension for ValueTags
through the type barrier, resulting in memory corruption and a potentially
Note: this issue only affects Firefox on ARM64 platforms.
o Bug 1640737
# CVE-2020-12418: Information disclosure due to manipulated URL object
Marcin 'Icewall' Noga of Cisco Talos
Manipulating individual parts of a URL object could have caused an
o Bug 1641303
# CVE-2020-12419: Use-after-free in nsGlobalWindowInner
When processing callbacks that occurred during window flushing in the parent
process, the associated window may die; causing a use-after-free condition.
This could have led to memory corruption and a potentially exploitable crash.
o Bug 1643874
# CVE-2020-12420: Use-After-Free when trying to connect to a STUN server
When trying to connect to a STUN server, a race condition could have caused a
use-after-free of a pointer, leading to memory corruption and a potentially
o Bug 1643437
# CVE-2020-15648: X-Frame-Options bypass using object or embed tags
Using object or embed tags, it was possible to frame other websites, even if
they disallowed framing using the X-Frame-Options header.
Note: This issue is pending a CVE assignment and will be updated when one is
o Bug 1644076
# CVE-2020-12402: RSA Key Generation vulnerable to side-channel attack
Sohaib ul Hassan, Iaroslav Gridin, Ignacio M. Delgado-Lozano, Cesar Pereida
Garcia, Jesus-Javier Chi-Dominguez, Alejandro Cabrera Aldaya, and Billy Bob
Brumley, Network and Information Security (NISEC) Group, Tampere
During RSA key generation, bignum implementations used a variation of the
Binary Extended Euclidean Algorithm which entailed significantly
input-dependent flow. This allowed an attacker able to perform
electromagnetic-based side channel attacks to record traces leading to the
recovery of the secret primes.
We would like to thank Sohaib ul Hassan for contributing a fix for this issue
Note: An unmodified Firefox browser does not generate RSA keys in normal
operation and is not affected, but products built on top of it might.
o Bug 1631597
# CVE-2020-12421: Add-On updates did not respect the same certificate trust
rules as software updates
Chuck Harmston, Robert Hardy
When performing add-on updates, certificate chains terminating in
non-built-in-roots were rejected (even if they were legitimately added by an
administrator.) This could have caused add-ons to become out-of-date silently
without notification to the user.
o Bug 1308251
# CVE-2020-12422: Integer overflow in nsJPEGEncoder::emptyOutputBuffer
caused an internal variable to overflow, resulting in an out of bounds write,
memory corruption, and a potentially exploitable crash.
o Bug 1450353
# CVE-2020-12423: DLL Hijacking due to searching %PATH% for a library
When the Windows DLL "webauthn.dll" was missing from the Operating System, and
a malicious one was placed in a folder in the user's %PATH%, Thunderbird may
have loaded the DLL, leading to arbitrary code execution.
Note: This issue only affects the Windows operating system; other operating
systems are unaffected.
o Bug 1642400
# CVE-2020-12424: WebRTC permission prompt could have been bypassed by a
compromised content process
When constructing a permission prompt for WebRTC, a URI was supplied from the
content process. This URI was untrusted, and could have been the URI of an
origin that was previously granted permission; bypassing the prompt.
o Bug 1562600
# CVE-2020-12425: Out of bound read in Date.parse()
Due to confusion processing a hyphen character in Date.parse(), a one-byte out
of bounds read could have occurred, leading to potential information
o Bug 1634738
# CVE-2020-12426: Memory safety bugs fixed in Thunderbird 78
Mozilla developers and community
Mozilla developers and community members Bob Clary, Benjamin Bouvier, Calixte
Denizet, Christian Holler reported memory safety bugs present in Thunderbird
77. 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
o Memory safety bugs fixed in Thunderbird 78
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