A flaw was found in sudo. When sudoers rules use NOTBEFORE or NOTAFTER time-based access restrictions with timestamps that omit the trailing 'Z' timezone indicator, the time evaluation relies on the TZ environment variable inherited from the calling user. Because sudo is a setuid-root program, an unprivileged local user can set TZ to an extreme timezone offset to shift the authorization window by up to approximately 25 hours, causing expired rules to be treated as valid. This allows the user to execute commands outside the intended time window. Authentication is not bypassed; only the time-based authorization check is affected.
Append the 'Z' timezone suffix to all NOTBEFORE and NOTAFTER timestamps in sudoers rules. For example, change 'NOTAFTER=20261231235959' to 'NOTAFTER=20261231235959Z'. Timestamps with the 'Z' suffix are interpreted as UTC via timegm() and are not affected by the TZ environment variable. Administrators can audit their sudoers configuration with: grep -rE 'NOT(BEFORE|AFTER)=' /etc/sudoers /etc/sudoers.d/ and verify that all timestamps end with 'Z'.