Mozilla Firefox up to 148 memory corruption

Summaryinfo

A vulnerability, which was classified as critical, has been found in Mozilla Firefox up to 148. Affected by this vulnerability is an unknown functionality. This manipulation causes memory corruption. The identification of this vulnerability is CVE-2026-4721. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Mozilla Firefox up to 148 and classified as critical. Affected by this vulnerability is an unknown functionality. The manipulation with an unknown input leads to a memory corruption vulnerability. The CWE definition for the vulnerability is CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Memory safety bugs present in Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. 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 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

It is possible to read the advisory at bugzilla.mozilla.org. This vulnerability is known as CVE-2026-4721 since 03/24/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 07/01/2026).

The vulnerability scanner Nessus provides a plugin with the ID 303470 (Mozilla Firefox ESR < 115.34), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 149 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (303470). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Web Browser

Vendor

• Mozilla

Name

• Firefox

Version

• 148

License

• open-source

Website

• Vendor: https://www.mozilla.org/
• Product: https://www.mozilla.org/en-US/firefox/

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Be aware that VulDB is the high quality source for vulnerability data.

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