Platform
firefox
Component
firefox
Fixed in
150
140.10
150
CVE-2026-6786 describes a collection of memory safety bugs discovered in Mozilla Firefox and Thunderbird. These bugs, characterized by evidence of memory corruption, pose a significant risk as they could potentially be exploited to execute arbitrary code. The vulnerability affects Firefox versions 140.9 through 149, Firefox ESR 140.9, Thunderbird versions 140.9 through 149, and Thunderbird ESR 140.9. A fix has been released in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
The core impact of CVE-2026-6786 stems from the memory corruption vulnerabilities. Successful exploitation could allow an attacker to gain control of the affected system, potentially leading to data theft, system compromise, or the execution of malicious code. While the specific attack vectors remain undefined in the public disclosure, the presence of memory corruption suggests a broad range of potential exploits, including buffer overflows and heap spraying. The blast radius extends to any user interacting with a vulnerable Firefox or Thunderbird instance, particularly those visiting malicious websites or handling compromised email attachments. The potential for remote code execution makes this a high-severity vulnerability.
CVE-2026-6786 was publicly disclosed on 2026-04-21. There is currently no indication of active exploitation in the wild, nor are there any publicly available proof-of-concept exploits. The vulnerability has not been added to the CISA KEV catalog. Given the nature of memory corruption vulnerabilities, it is likely that security researchers are actively investigating potential exploitation techniques.
Exploit Status
EPSS
0.06% (19% percentile)
The primary mitigation for CVE-2026-6786 is to immediately upgrade to a patched version of Firefox or Thunderbird. Upgrade to Firefox 150, Firefox ESR 140.10, Thunderbird 150, or Thunderbird 140.10. If immediate upgrading is not possible due to compatibility issues or testing requirements, consider implementing stricter content security policies (CSP) to limit the execution of untrusted scripts. Monitor network traffic for suspicious activity, particularly connections to unknown or untrusted domains. Review and update firewall rules to restrict access to vulnerable services. After upgrading, confirm the fix by verifying the version number and checking for any unexpected behavior or error messages.
Update to version 150 or later of Firefox or version 140.10 or later of Firefox ESR to mitigate the memory corruption vulnerability. Ensure you apply the latest security updates to protect against potential exploits.
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CVE-2026-6786 is a memory corruption vulnerability affecting Firefox and Thunderbird versions 140.9 through 149 and their ESR counterparts. Exploitation could lead to arbitrary code execution.
You are affected if you are using Firefox versions 140.9 through 149 or Firefox ESR 140.9. Upgrade to Firefox 150 or Firefox ESR 140.10 to mitigate the risk.
Upgrade to Firefox version 150 or Firefox ESR 140.10. Ensure automatic updates are enabled to receive future security patches.
There is currently no evidence of active exploitation in the wild, but the vulnerability's nature suggests potential for future attacks.
Refer to the Mozilla Security Advisories page for the official advisory: https://www.mozilla.org/en-US/security/advisories/
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