CVE-2026-0818

Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If the user had additionally allowed loading of the remote content referenced by the outer email message, and the email was crafted by the sender using a combination of CSS rules and fonts and animations, then it was possible to extract the secret contents of the email. This vulnerability affects Thunderbird < 147.0.1 and Thunderbird < 140.7.1.(CVE-2026-0818)

Heap buffer overflow in libvpx. This vulnerability affects Firefox < 147.0.4, Firefox ESR < 140.7.1, Firefox ESR < 115.32.1, Thunderbird < 140.7.2, and Thunderbird < 147.0.2.(CVE-2026-2447)

Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If the user had additionally allowed loading of the remote content referenced by the outer email message, and the email was crafted by the sender using a combination of CSS rules and fonts and animations, then it was possible to extract the secret contents of the email. This vulnerability affects Thunderbird < 147.0.1 and Thunderbird < 140.7.1.(CVE-2026-0818)

Heap buffer overflow in libvpx. This vulnerability affects Firefox < 147.0.4, Firefox ESR < 140.7.1, Firefox ESR < 115.32.1, Thunderbird < 140.7.2, and Thunderbird < 147.0.2.(CVE-2026-2447)

Incorrect boundary conditions in the WebRTC: Audio/Video component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2757)

Use-after-free in the JavaScript: GC component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2758)

Incorrect boundary conditions in the Graphics: ImageLib component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2759)

Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2760)

Sandbox escape in the Graphics: WebRender component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2761)

Integer overflow in the JavaScript: Standard Library component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2762)

Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2763)

JIT miscompilation, use-after-free in the JavaScript Engine: JIT component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2764)

Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2765)

Use-after-free in the JavaScript Engine: JIT component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2766)

Use-after-free in the JavaScript: WebAssembly component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2767)

Sandbox escape in the Storage: IndexedDB component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2768)

Use-after-free in the Storage: IndexedDB component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2769)

Use-after-free in the DOM: Bindings (WebIDL) component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.(CVE-2026-2770)

Undefined behavior in the DOM: Core & HTML component. This vulnerability affects…

When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If the user had additionally allowed loading of the remote content referenced by the outer email message, and the email was crafted by the sender using a combination of CSS rules and fonts and animations, then it was possible to extract the secret contents of the email. This vulnerability was fixed in Thunderbird 147.0.1 and Thunderbird 140.7.1.

• rebase from Thunderbird 115.4.1 to 140.12.0 ESR

• CVE-2022-3032: When receiving an HTML email that contained an iframe element, which used a srcdoc attribute to define the inner HTML document, remote objects specified in the nested document, for example images or videos, were not blocked

• CVE-2023-0430: Certificate OCSP revocation status was not checked when verifying S/Mime signatures

• CVE-2023-0547: OCSP revocation status of recipient certificates was not checked when sending S/Mime encrypted email, and revoked certificates would be accepted

• CVE-2023-0616: If a MIME email combines OpenPGP and OpenPGP MIME data in a certain way Thunderbird repeatedly attempts to process and display the message, which could cause Thunderbird's user interface to lock up and no longer respond to the user's actions

• CVE-2023-1945: Unexpected data returned from the Safe Browsing API could have led to memory corruption and a potentially exploitable crash

• CVE-2023-4573: When receiving rendering data over IPC mStream could have been destroyed when initialized, which could have led to a use-after-free causing a potentially exploitable crash

• CVE-2023-4574: When creating a callback over IPC for showing the Color Picker window, multiple of the same callbacks could have been created at a time and eventually all simultaneously destroyed as soon as one of the callbacks finished

• CVE-2023-4575: When creating a callback over IPC for showing the File Picker window, multiple of the same callbacks could have been created at a time and eventually all simultaneously destroyed as soon as one of the callbacks finished

• CVE-2023-4577: When UpdateRegExpStatics attempted to access initialStringHeap it could already have been garbage collected prior to entering the function, which could potentially have led to an exploitable crash

• CVE-2023-4578: When calling JS::CheckRegExpSyntax a Syntax Error could have been set which would end in calling convertToRuntimeErrorAndClear. A path in the function could attempt to allocate memory when none is available which would have caused a newly created Out of Memory exception to be mishandled as a Syntax Error

• CVE-2023-4580: Push notifications stored on disk in private browsing mode were not being encrypted potentially allowing the leak of sensitive information

• CVE-2023-4581: Excel .xll add-in files did not have a blocklist entry in Firefox's executable blocklist which allowed them to be downloaded without any warning of their potential harm

• CVE-2023-5169: A compromised content process could have provided malicious data in a PathRecording resulting in an out-of-bounds write, leading to a potentially exploitable crash in a privileged process

• CVE-2023-5171: During Ion compilation, a Garbage Collection could have resulted in a use-after-free condition, allowing an attacker to write two NUL bytes, and cause a potentially exploitable crash

• CVE-2023-5724: Drivers are not always robust to extremely large draw calls and in some cases this scenario could have led to a crash

• CVE-2023-5725: A malicious installed WebExtension could open arbitrary URLs, which under the right circumstance could be leveraged to collect sensitive user data

• CVE-2023-5732: An attacker could have created a malicious link using bidirectional characters to spoof the location in the address bar when visited

• CVE-2023-6204: On some systems—depending on the graphics settings and drivers—it was possible to force an out-of-bounds read and leak memory data into the images created on the canvas element

• CVE-2023-6205: It was possible to cause the use of a MessagePort after it had already been freed, which could potentially have led to an exploitable crash

• CVE-2023-6206: The black fade animation when exiting fullscreen is roughly the length of the anti-clickjacking delay on permission prompts

• CVE-2023-6207: Ownership…

CSS-based exfiltration of the content from partially encrypted emails when allowing remote content. (CVE-2026-0818)

These are all security issues fixed in the MozillaThunderbird-140.7.1-1.1 package on the GA media of openSUSE Tumbleweed.

This update for MozillaThunderbird fixes the following issues:

Changes in MozillaThunderbird:

• Mozilla Thunderbird 140.8.1 ESR

  • Add mail.openpgp.load_untested_gpgme_version to load untested GPGME version

• Mozilla Thunderbird 140.8.0 ESR MFSA 2026-17 (boo#1258568)

  • CVE-2026-2757 (bmo#2001637) Incorrect boundary conditions in the WebRTC: Audio/Video component
  • CVE-2026-2758 (bmo#2009608) Use-after-free in the JavaScript: GC component
  • CVE-2026-2759 (bmo#2010933) Incorrect boundary conditions in the Graphics: ImageLib component
  • CVE-2026-2760 (bmo#2011062) Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component
  • CVE-2026-2761 (bmo#2011063) Sandbox escape in the Graphics: WebRender component
  • CVE-2026-2762 (bmo#2011649) Integer overflow in the JavaScript: Standard Library component
  • CVE-2026-2763 (bmo#2012018) Use-after-free in the JavaScript Engine component
  • CVE-2026-2764 (bmo#2012608) JIT miscompilation, use-after-free in the JavaScript Engine: JIT component
  • CVE-2026-2765 (bmo#2013562) Use-after-free in the JavaScript Engine component
  • CVE-2026-2766 (bmo#2013583) Use-after-free in the JavaScript Engine: JIT component
  • CVE-2026-2767 (bmo#2013741) Use-after-free in the JavaScript: WebAssembly component
  • CVE-2026-2768 (bmo#2014101) Sandbox escape in the Storage: IndexedDB component
  • CVE-2026-2769 (bmo#2014550) Use-after-free in the Storage: IndexedDB component
  • CVE-2026-2770 (bmo#2014585) Use-after-free in the DOM: Bindings (WebIDL) component
  • CVE-2026-2771 (bmo#2014593) Undefined behavior in the DOM: Core & HTML component
  • CVE-2026-2772 (bmo#2014827) Use-after-free in the Audio/Video: Playback component
  • CVE-2026-2773 (bmo#2014832) Incorrect boundary conditions in the Web Audio component
  • CVE-2026-2774 (bmo#2014883) Integer overflow in the Audio/Video component
  • CVE-2026-2775 (bmo#2015199) Mitigation bypass in the DOM: HTML Parser component
  • CVE-2026-2776 (bmo#2015266) Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software
  • CVE-2026-2777 (bmo#2015305) Privilege escalation in the Messaging System component
  • CVE-2026-2778 (bmo#2016358) Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component
  • CVE-2026-2779 (bmo#1164141) Incorrect boundary conditions in the Networking: JAR component
  • CVE-2026-2780 (bmo#2007829) Privilege escalation in the Netmonitor component
  • CVE-2026-2781 (bmo#2009552) Integer overflow in the Libraries component in NSS
  • CVE-2026-2782 (bmo#2010743) Privilege escalation in the Netmonitor component
  • CVE-2026-2783 (bmo#2010943) Information disclosure due to JIT miscompilation in the JavaScript Engine: JIT component
  • CVE-2026-2784 (bmo#2012984) Mitigation bypass in the DOM: Security component
  • CVE-2026-2785 (bmo#2013549) Invalid pointer in the JavaScript Engine component
  • CVE-2026-2786 (bmo#2013612) Use-after-free in the JavaScript Engine component
  • CVE-2026-2787 (bmo#2014560) Use-after-free in the DOM: Window and Location component
  • CVE-2026-2788 (bmo#2014824) Incorrect boundary conditions in the Audio/Video: GMP component
  • CVE-2026-2789 (bmo#2015179) Use-after-free in the Graphics: ImageLib component
  • CVE-2026-2790 (bmo#2008426) Same-origin policy bypass in the Networking: JAR component
  • CVE-2026-2791 (bmo#2015220) Mitigation bypass in the Networking: Cache component
  • CVE-2026-2792 (bmo#2008912, bmo#2010050, bmo#2010275, bmo#2012331) Memory safety bugs fixed in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148
  • CVE-2026-2793 (bmo#2015196, bmo#2016423, bmo#2016498) Memory safety bugs fixed in Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and…

This update for MozillaThunderbird fixes the following issues:

Update to Mozilla Thunderbird 140.7.1 MFSA 2026-08 (bsc#1257397):

• CVE-2026-0818: CSS-based exfiltration of the content from partially encrypted emails when allowing remote content