RRD::CGI::Image versions through 0.01 for Perl pass CGI query parameters containting "tz" to tzset(), , so a FIFO or device path blocks the CGI process. The normalize_params method sends any query key matching /tz/i to tz(), which sets $ENV{TZ} to that value, with no validation. It then calls tzset(). glibc treats a TZ value starting with / or : as a file path and opens it, so a value naming a FIFO or a blocking device stalls the process inside tzset().
https://security.metacpan.org/patches/R/RRD-CGI-Image/0.01/CVE-2026-123776-r1.patch
https://rt.cpan.org/Ticket/Display.html?id=182627
https://man7.org/linux/man-pages/man3/tzset.3.html