B737-800 flight crew reported pressurization malfunction during descent.

Narrative

During a normal descent we stopped at ATC assigned altitude FL260. Both pilot's front panel 'CABIN ALTITUDE' red lights illuminated as well as the 'CABIN ALT' warning horn sounding. Both pilots donned O2 masks and established communications; and I silenced the horn. FO (First Officer) was PF (Pilot Flying). I grabbed the QRC card. We both agreed that the cabin altitude was indicating about 10;000-10;500 ft. and I had the correct checklist item in hand. Step #4 selecting the cabin outflow valve to full close in manual regained pressurization control. Informed ATC we were dealing with a pressurization problem and needed lower now. ATC assigned 10;000 ft. Since I had control of the cabin controller in manual and we were already descending; I did not declare an emergency. Followed the QRH procedure for controlling the cabin in manual till landing. There were no casual factors involved with this event.I have no suggestions for this event. The pressurization was working normal from takeoff.; cruise and the initial descent. Seems like we may have had a failure of both a primary and secondary auto controller at the same time. That's why we didn't get any alerts or warnings till the cabin altitude reached 10;000 ft. Initial check at the TOD showed the auto controller was set correctly for a landing at ZZZ.