CVE-2026-91142 is an integer overflow vulnerability in Cockpit's do_lastlog() function affecting ILP32 (32-bit Integer, Long, Pointer) builds. The flaw arises from improper offset calculation for lastlog entries, where a low-privileged authenticated user with a specially provisioned large UID can cause the offset to wrap around. This results in misaddressed lastlog entries, allowing unauthorized cross-user reads and writes of legacy lastlog records. The vulnerability impacts confidentiality and integrity of login accounting data but does not lead to code execution or privilege escalation. Exploitation requires local access with authentication and high attack complexity.

The vulnerability allows a low-privileged authenticated user to read and modify other users' lastlog records due to an integer overflow in offset calculation. This can lead to disclosure and alteration of sensitive login accounting information. There is no impact on availability or possibility of code execution or privilege escalation.

No official fix or patch link is provided in the advisory. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Exploitation requires a specially provisioned large UID and local authenticated access with high attack complexity. Monitor vendor updates for patches or mitigations. No urgent action is indicated beyond applying vendor fixes when available.