Red Hat Product Security issued advisory RHSA-2025:8639 addressing two out-of-bounds access vulnerabilities in Firefox and Thunderbird (CVE-2025-4918 and CVE-2025-4919). These vulnerabilities relate to improper memory access when resolving Promise objects and optimizing linear sums, which could lead to potential security risks. The advisory applies to Red Hat Enterprise Linux Server AUS 8.2 x86_64 and provides updated Firefox packages (version 128.10.1-1.el8_2) to fix these issues. No CVSS scores are provided in the advisory, but the severity is rated as important by Red Hat.

The vulnerabilities involve out-of-bounds memory access, which can lead to memory corruption or crashes in Firefox and Thunderbird. Such issues may be exploitable to cause denial of service or potentially other impacts depending on the context of exploitation. Red Hat classifies the security impact as important, indicating a significant but not critical risk level.

Red Hat has released updated Firefox packages (version 128.10.1-1.el8_2) for Red Hat Enterprise Linux 8.2 AUS to address these vulnerabilities. Users should apply these official updates promptly to remediate the issues. Detailed update instructions are available at https://access.redhat.com/articles/11258. No additional mitigations are specified or required beyond applying the vendor-provided update.