A stored SQL injection vulnerability in Koha through 24.11.17, 25.05.12, 25.11.06, and 26.05.01 allows authenticated staff with the borrowers => edit_borrowers permission to cause a time-based denial of service by storing a SQL payload in a patron lang field. The value is concatenated raw into a subquery in Koha::AdditionalContents->search_for_display when an issue slip is printed for the affected patron. The 25-character column length limits exploitation to timing attacks; data extraction is not practical. The stored payload executes on each subsequent issue-slip print, scaling linearly with the SLEEP value and the number of slip-news rows.