Threat database

When Thunderbird asked for a security device password (for example a smartcard PIN or the Primary Password) while decrypting an S/MIME message, the message load could finish or be cancelled while the prompt was open. This freed the message decoder while it was still in use, causing a use-after-free and a potentially exploitable crash. This vulnerability was fixed in Thunderbird 158.0.1.

When authenticating to a POP3 or SMTP server using NTLM, Thunderbird did not check whether the server's challenge was valid base64. A malicious server could send a challenge that caused Thunderbird to include uninitialized heap memory in its NTLM response, disclosing that memory to the server. A challenge consisting only of base64 padding also caused an out-of-bounds read, crashing Thunderbird. This affected accounts configured to use NTLM or GSSAPI authentication. The uninitialized memory disclosure only affected NTLM. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

Thunderbird did not escape attribute values when serializing outgoing XMPP stanzas. Because values from incoming requests were echoed back in automatic replies, a remote XMPP user could send a crafted request that caused Thunderbird to inject arbitrary stanzas into the user's connection, which the server would then process as if sent by the user. This could be used to send messages or change contact and subscription settings on behalf of the user, without any interaction. This bug only affects Thunderbird's chat feature with XMPP accounts. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 158.0.1 and Thunderbird 158.0.1.

Uninitialized memory in the Audio/Video: cubeb component. This vulnerability was fixed in Firefox 158.0.1 and Thunderbird 158.0.1.

Incorrect boundary conditions in the SVG component. This vulnerability was fixed in Firefox 158.0.1 and Thunderbird 158.0.1.

Mozilla blocked compromised intermediate eMudhra certificates via OneCRL on the 17th of October which was distributed to clients via RemoteSettings the same day. This update contains the updated OneCRL block list, ensuring clients will block the compromised certificates even if RemoteSettings is disabled by policy or otherwise unavailable in the user's network environment. This vulnerability was fixed in Firefox 158.0.1, Firefox ESR 153.5.1, and Firefox ESR 115.43.1.

A malicious, compromised, or MITM-controlled Exchange server can return a single well-formed SOAP response containing an element with enough attributes to keep Thunderbird's main thread CPU-bound for seconds to hours. This vulnerability was fixed in Thunderbird 158 and Thunderbird 153.5.

Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks. On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent heap allocations. This vulnerability was fixed in Thunderbird 158.

Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox ESR 153.5 and Thunderbird 153.5.

Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox ESR 153.5 and Thunderbird 153.5.

Denial-of-service in the Printing: Output component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Mitigation bypass in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.

Race condition in the Networking: DNS component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.

CVE-2026-109778 is a high-severity privilege escalation vulnerability in the WebExtensions component of Mozilla Firefox and Thunderbird. It allows an attacker to escalate privileges, potentially leading to full system compromise. The issue affects Firefox versions prior to 158 and Thunderbird versions prior to 158. Mozilla has released official fixes in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Information disclosure in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

CVE-2026-109776 is a medium-severity race condition vulnerability in the XPCOM component of Mozilla Firefox and Thunderbird. It affects Firefox versions prior to 158 and Thunderbird versions prior to 158. The vulnerability allows for limited confidentiality and integrity impact but does not affect availability. It requires network attack vector, high attack complexity, no privileges, and user interaction. Official fixes are available in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Denial-of-service in the WebRTC component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Invalid pointer, undefined behavior in the DOM: Notifications component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.