CVE-2025-26696

Certain crafted MIME email messages that claimed to contain an encrypted OpenPGP message, which instead contained an OpenPGP signed message, were wrongly shown as being encrypted. This vulnerability was fixed in Thunderbird 136 and Thunderbird 128.8.

Mozilla Thunderbird is a standalone mail and newsgroup client.

Security Fix(es):

• firefox: thunderbird: Memory safety bugs fixed in Firefox 136, Thunderbird 136, Firefox ESR 128.8, and Thunderbird 128.8 (CVE-2025-1938)
• firefox: thunderbird: Memory safety bugs fixed in Firefox 136, Thunderbird 136, Firefox ESR 115.21, Firefox ESR 128.8, and Thunderbird 128.8 (CVE-2025-1937)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

• 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…

This update for MozillaThunderbird fixes the following issues:

Updated to Mozilla Thunderbird 128.8 MFSA 2025-18 (bsc#1237683):

• CVE-2024-43097: Overflow when growing an SkRegion's RunArray
• CVE-2025-1930: AudioIPC StreamData could trigger a use-after-free in the Browser process
• CVE-2025-1931: Use-after-free in WebTransportChild
• CVE-2025-1932: Inconsistent comparator in XSLT sorting led to out-of-bounds access
• CVE-2025-1933: JIT corruption of WASM i32 return values on 64-bit CPUs
• CVE-2025-1934: Unexpected GC during RegExp bailout processing
• CVE-2025-1935: Clickjacking the registerProtocolHandler info-bar
• CVE-2025-1936: Adding %00 and a fake extension to a jar: URL changed the interpretation of the contents
• CVE-2025-1937: Memory safety bugs fixed in Firefox 136, Thunderbird 136, Firefox ESR 115.21, Firefox ESR 128.8, and Thunderbird 128.8
• CVE-2025-1938: Memory safety bugs fixed in Firefox 136, Thunderbird 136, Firefox ESR 128.8, and Thunderbird 128.8
• CVE-2025-26695: Downloading of OpenPGP keys from WKD used incorrect padding
• CVE-2025-26696: Crafted email message incorrectly shown as being encrypted

Other fixes:

• Opening an .EML file in profiles with many folders could take a long time.
• Users with many folders experienced poor performance when resizing message panes. *'Replace' button in compose window was overwritten when the window was narrow.
• Export to mobile did not work when 'Use default server' was selected.
• 'Save Link As' was not working in feed web content.

Multiple security issues were discovered in Thunderbird. If a user were tricked into opening a specially crafted website in a browsing context, an attacker could potentially exploit these to cause a denial of service, obtain sensitive information, bypass security restrictions, cross-site tracing, or execute arbitrary code.