Mozilla Firefox vulnerabilities

CVE-2025-6427 [CRITICAL] CWE-693 CVE-2025-6427: An attacker was able to bypass the `connect-src` directive of a Content Security Policy by manipulat An attacker was able to bypass the `connect-src` directive of a Content Security Policy by manipulating subdocuments. This would have also hidden the connections from the Network tab in Devtools. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVE-2025-6433 [CRITICAL] CWE-295 CVE-2025-6433: If a user visited a webpage with an invalid TLS certificate, and granted an exception, the webpage w If a user visited a webpage with an invalid TLS certificate, and granted an exception, the webpage was able to provide a WebAuthn challenge that the user would be prompted to complete. This is in violation of the WebAuthN spec which requires "a secure transport established without errors". This vulnerability was fixed in Firefox 140 and Thunderbird

CVE-2025-6424 [CRITICAL] CWE-416 CVE-2025-6424: A use-after-free in FontFaceSet resulted in a potentially exploitable crash. This vulnerability was A use-after-free in FontFaceSet resulted in a potentially exploitable crash. This vulnerability was fixed in Firefox 140, Firefox ESR 115.25, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

CVE-2025-6436 [HIGH] CWE-119 CVE-2025-6436: Memory safety bugs present in Firefox 139 and Thunderbird 139. Some of these bugs showed evidence of Memory safety bugs present in Firefox 139 and Thunderbird 139. 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 code. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVE-2025-6426 [HIGH] CWE-345 CVE-2025-6426: The executable file warning did not warn users before opening files with the `terminal` extension. The executable file warning did not warn users before opening files with the `terminal` extension. *This bug only affects Firefox for macOS. Other versions of Firefox are unaffected.*. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

CVE-2025-6435 [HIGH] CWE-434 CVE-2025-6435: If a user saved a response from the Network tab in Devtools using the Save As context menu option, t If a user saved a response from the Network tab in Devtools using the Save As context menu option, that file may not have been saved with the `.download` file extension. This could have led to the user inadvertently running a malicious executable. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVE-2025-6432 [HIGH] CWE-200 CVE-2025-6432: When Multi-Account Containers was enabled, DNS requests could have bypassed a SOCKS proxy when the d When Multi-Account Containers was enabled, DNS requests could have bypassed a SOCKS proxy when the domain name was invalid or the SOCKS proxy was not responding. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVE-2025-6425 [MEDIUM] CWE-200 CVE-2025-6425: An attacker who enumerated resources from the WebCompat extension could have obtained a persistent U An attacker who enumerated resources from the WebCompat extension could have obtained a persistent UUID that identified the browser, and persisted between containers and normal/private browsing mode, but not profiles. This vulnerability was fixed in Firefox 140, Firefox ESR 115.25, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

CVE-2025-6434 [MEDIUM] CWE-1021 CVE-2025-6434: The exception page for the HTTPS-Only feature, displayed when a website is opened via HTTP, lacked a The exception page for the HTTPS-Only feature, displayed when a website is opened via HTTP, lacked an anti-clickjacking delay, potentially allowing an attacker to trick a user into granting an exception and loading a webpage over HTTP. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVE-2025-6429 [MEDIUM] CWE-116 CVE-2025-6429: Firefox could have incorrectly parsed a URL and rewritten it to the youtube.com domain when parsing Firefox could have incorrectly parsed a URL and rewritten it to the youtube.com domain when parsing the URL specified in an `embed` tag. This could have bypassed website security checks that restricted which domains users were allowed to embed. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

CVE-2025-6430 [MEDIUM] CWE-79 CVE-2025-6430: When a file download is specified via the `Content-Disposition` header, that directive would be igno When a file download is specified via the `Content-Disposition` header, that directive would be ignored if the file was included via a ` ` or ` ` tag, potentially making a website vulnerable to a cross-site scripting attack. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

CVE-2025-6428 [MEDIUM] CWE-601 CVE-2025-6428: When a URL was provided in a link querystring parameter, Firefox for Android would follow that URL i When a URL was provided in a link querystring parameter, Firefox for Android would follow that URL instead of the correct URL, potentially leading to phishing attacks. *This bug only affects Firefox for Android. Other versions of Firefox are unaffected.*. This vulnerability was fixed in Firefox 140.

CVE-2025-6431 [MEDIUM] CWE-285 CVE-2025-6431: When a link can be opened in an external application, Firefox for Android will, by default, prompt t When a link can be opened in an external application, Firefox for Android will, by default, prompt the user before doing so. An attacker could have bypassed this prompt, potentially exposing the user to security vulnerabilities or privacy leaks in external applications. *This bug only affects Firefox for Android. Other versions of Firefox are unaffect

CVE-2025-49709 [CRITICAL] CWE-787 CVE-2025-49709: Certain canvas operations could have lead to memory corruption. This vulnerability was fixed in Fire Certain canvas operations could have lead to memory corruption. This vulnerability was fixed in Firefox 139.0.4.

CVE-2025-49710 [CRITICAL] CWE-190 CVE-2025-49710: An integer overflow was present in `OrderedHashTable` used by the JavaScript engine. This vulnerabil An integer overflow was present in `OrderedHashTable` used by the JavaScript engine. This vulnerability was fixed in Firefox 139.0.4.

CVE-2025-5268 [HIGH] CWE-119 CVE-2025-5268: Memory safety bugs present in Firefox 138, Thunderbird 138, Firefox ESR 128.10, and Thunderbird 128. Memory safety bugs present in Firefox 138, Thunderbird 138, Firefox ESR 128.10, and Thunderbird 128.10. 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 code. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunder

CVE-2025-5272 [HIGH] CWE-787 CVE-2025-5272: Memory safety bugs present in Firefox 138 and Thunderbird 138. Some of these bugs showed evidence of Memory safety bugs present in Firefox 138 and Thunderbird 138. 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 code. This vulnerability was fixed in Firefox 139 and Thunderbird 139.

CVE-2025-5270 [HIGH] CWE-319 CVE-2025-5270: In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled. This vul In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled. This vulnerability was fixed in Firefox 139 and Thunderbird 139.

CVE-2025-5269 [HIGH] CWE-787 CVE-2025-5269: Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10. This bug showed evidence of Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.11 and Thunderbird 128.11.

CVE-2025-5265 [MEDIUM] CWE-77 CVE-2025-5265: Due to insufficient escaping of the ampersand character in the “Copy as cURL” feature, an attacker c Due to insufficient escaping of the ampersand character in the “Copy as cURL” feature, an attacker could trick a user into using this command, potentially leading to local code execution on the user's system. *This bug only affects Firefox for Windows. Other versions of Firefox are unaffected.*. This vulnerability was fixed in Firefox 139, Firefox ESR