Medium (6.1). EPSS 0.7% chance of exploitation in the next 30 days.
Set-Cookie response headers were being incorrectly honored in multipart HTTP responses. If an attacker could control the Content-Type response header, as well as control part of the response body, they could inject Set-Cookie response headers that would have been honored by the browser. This vulnerability affects Firefox < 123, Firefox ESR < 115.8, and Thunderbird < 115.8.
Severity
CVSS 3.1
6.1 medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS
0.7% chance of exploitation in the next 30 days; higher than 54% of CVEs (scores of 2026-10-31)