CVE-2026-12327: mozilla firefox

Vulnerability summary

CVE-2026-12327 is a high (CVSS 8.1) vulnerability in mozilla firefox. EPSS estimates a 0.41% chance of exploitation in the next 30 days, higher than 33.4% of scored vulnerabilities.

Timeline

1. 16-06-2026
   PublishedVulnerability first disclosed.
2. 17-06-2026
   Last modifiedVulnerability information updated.

Description

Memory safety bugs present in Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151 and Thunderbird 151. 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 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

• CWE-119Improper Restriction of Operations within the Bounds of a Memory BufferThe product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.