Mozilla、Thunderbird 52.8.0修正版リリースで、数多くのセキュリティ脆弱性に対応。早めのアップデートを！

Mozillaは5月19日（現地時間5月18日）、Windows PC、MacおよびLinux向けメールクライアントThunderbirdの修正バージョン「Thunderbird 52.8.0」をリリースしました。

今回のアップデートでは、さまざまなセキュリティ修正が行われています。

今バージョンでのセキュリティ脆弱性についての対応は、Mozillaが公開したセキュリティアドバイザリによると全部で13件となっています。その内訳は、重要度区分最高ランクの［critical］が２件、次いで高い［high］が４件、中である［moderate］が６件、低である［low］が１件となっています。数多くのセキュリティ修正が含まれており、早めのアップデートを行うことが推奨されます。

また、既知の問題点として未解決の「S/MIME暗号化またはPGP暗号化（Enigmailアドオン経由）を使用」している場合の解決方法については、「The Mozilla Thunderbird Blog」に掲載されているブログの指示に従うことを推奨しています。

Thunderbird 52.8.0のリリースノート

修正

Various security fixes

セキュリティ修正

［critical］CVE-2018-5183: Backport critical security fixes in Skia
Mozilla developers backported selected changes in the Skia library. These changes correct memory corruption issues including invalid buffer reads and writes during graphic operations.
［critical］CVE-2018-5150: Memory safety bugs fixed in Firefox 60, Firefox ESR 52.8, and Thunderbird 52.8
Mozilla developers and community members Christoph Diehl, Randell Jesup, Tyson Smith, Alex Gaynor, Ronald Crane, Julian Hector, Kannan Vijayan, and Jason Kratzer reported memory safety bugs present in Firefox 59, Firefox ESR 52.7, and Thunderbird 52.7. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code.
［high］CVE-2018-5184: Full plaintext recovery in S/MIME via chosen-ciphertext attack
Using remote content in encrypted messages can lead to the disclosure of plaintext.
［high］CVE-2018-5154: Use-after-free with SVG animations and clip paths
A use-after-free vulnerability can occur while enumerating attributes during SVG animations with clip paths. This results in a potentially exploitable crash.
［high］CVE-2018-5155: Use-after-free with SVG animations and text paths
A use-after-free vulnerability can occur while adjusting layout during SVG animations with text paths. This results in a potentially exploitable crash.
［high］CVE-2018-5159: Integer overflow and out-of-bounds write in Skia
An integer overflow can occur in the Skia library due to 32-bit integer use in an array without integer overflow checks, resulting in possible out-of-bounds writes. This could lead to a potentially exploitable crash triggerable by web content.
［moderate］CVE-2018-5161: Hang via malformed headers
Crafted message headers can cause a Thunderbird process to hang on receiving the message.
［moderate］CVE-2018-5162: Encrypted mail leaks plaintext through src attribute
Plaintext of decrypted emails can leak through the src attribute of remote images, or links.
［moderate］CVE-2018-5170: Filename spoofing for external attachments
It is possible to spoof the filename of an attachment and display an arbitrary attachment name. This could lead to a user opening a remote attachment which is a different file type than expected.
［moderate］CVE-2018-5168: Lightweight themes can be installed without user interaction
Sites can bypass security checks on permissions to install lightweight themes by manipulating the baseURI property of the theme element. This could allow a malicious site to install a theme without user interaction which could contain offensive or embarrassing images.
［moderate］CVE-2018-5174: Windows Defender SmartScreen UI runs with less secure behavior for downloaded files in Windows 10 April 2018 Update
In the Windows 10 April 2018 Update, Windows Defender SmartScreen honors the SEE_MASK_FLAG_NO_UI flag associated with downloaded files and will not show any UI. Files that are unknown and potentially dangerous will be allowed to run because SmartScreen will not prompt the user for a decision, and if the user is offline all files will be allowed to be opened because Windows won’t prompt the user to ask what to do. Firefox incorrectly sets this flag when downloading files, leading to less secure behavior from SmartScreen.
Note: this issue only affects Windows 10 users running the April 2018 update or later. It does not affect other Windows users or other operating systems.
［moderate］CVE-2018-5178: Buffer overflow during UTF-8 to Unicode string conversion through legacy extension
A buffer overflow was found during UTF8 to Unicode string conversion within JavaScript with extremely large amounts of data. This vulnerability requires the use of a malicious or vulnerable legacy extension in order to occur.
［low］CVE-2018-5185: Leaking plaintext through HTML forms
Plaintext of decrypted emails can leak through by user submitting an embedded form.

既知の問題点

未解決

S/MIME 暗号化あるいは PGP 暗号化 (後者は Enigmail アドオンによる) を利用している場合、Efail 脆弱性に関するエントリを参照されたい

なお、Thunderbird 52.8.0はWindows PC、Mac、およびLinux版が公開されており、Mozillaの「Thunderbirdダウンロード」サイトよりダウンロード可能となっています。既存のThunderbird 5以降を使用しているユーザであれば自動アップデート経由で通知されます。通知が待てない場合には、ヘルプメニューの「Thunderbird について」より手動でアップデートすることも可能となっています。