519400 2026-04-25 12:32:05 +0000 Lock screen unresponsive after waking from sleep; requires "Switch User" to SDDM to log in 2026-07-15 20:32:35 +0000 1 1 4 Plasma plasmashell Screen locking 6.6.4 Arch Linux Linux RESOLVED DUPLICATE 521900 NOR major 1.0 0 hi plasma-bugs-null kdedev nate wazhai 0 oldest_to_newest 2512077 0 191787 hi 2026-04-25 12:32:05 +0000 Created attachment 191787 kscreenlocker logs gathered using "journalctl -b 0 | grep -i kscreenlocker" SUMMARY After locking the screen and putting the system to sleep, the lock screen becomes unresponsive upon waking up. It will not accept input or unlock the session. Clicking the "Switch User" button drops back to the initial SDDM login screen, which functions correctly and allows successfully logging back into the session. STEPS TO REPRODUCE 1. Lock the Plasma session. 2. Suspend the system to sleep. 3. Wake the system. 4. Attempt to type the password and unlock the screen Reproducibility: Sometimes (Intermittent) OBSERVED RESULT The lock screen won't unlock. EXPECTED RESULT The lock screen should accept the password and successfully unlock the existing session. SOFTWARE/OS VERSIONS Linux/KDE Plasma: 6.19.11-arch1-1 (64-bit) KDE Plasma Version: 6.6.4 KDE Frameworks Version: 6.25.0 Qt Version: 6.11.0 ADDITIONAL INFORMATION Note on User Impact: While the "Switch User" workaround technically exists, it is highly unintuitive. For months before discovering it, my only perceived way out of this freeze was a hard hardware shutdown via the power button, resulting in lost sessions. Most regular users encountering this will likely do the same, assuming a total system lockup. 2514117 1 kdedev 2026-05-06 16:56:07 +0000 Logs for searchability Apr 25 10:44:50 Rlyeh kscreenlocker_greet[19406]: pam_unix(kde:auth): unexpected response from failed conversation function Apr 25 10:44:50 Rlyeh kscreenlocker_greet[19406]: pam_unix(kde:auth): conversation failed Apr 25 10:44:50 Rlyeh kscreenlocker_greet[19406]: pam_unix(kde:auth): auth could not identify password for [cthulhu] Apr 25 10:45:02 Rlyeh kscreenlocker_greet[19406]: pam_unix(kde:auth): unexpected response from failed conversation function Apr 25 10:45:02 Rlyeh kscreenlocker_greet[19406]: pam_unix(kde:auth): conversation failed Apr 25 10:45:02 Rlyeh kscreenlocker_greet[19406]: pam_unix(kde:auth): auth could not identify password for [cthulhu] Apr 25 17:54:08 Rlyeh kscreenlocker_greet[19406]: [PAM worker kde] Authentication attempt too soon. This shouldn't happen! 2514119 2 kdedev 2026-05-06 16:57:00 +0000 Thanks for the bug report. The logs indicate this is related to bug 481808, but a worse manifestation Please can you run the following: ❯ QT_LOGGING_RULES=kscreenlocker_greet.debug=true /opt/kde6/lib/libexec/kscreenlocker_greet --testing and reproduce the issue. Also can you share /etc/pam.d/kde (they differ per distro) and output of `faillock --user $USER` Thanks 2514355 3 hi 2026-05-07 14:16:11 +0000 Hi, thanks for looking into this! Here is the output you requested. I specifically waited for the bug to trigger again so I could catch the exact output when it happens. Here is all the output: `/usr/lib/kscreenlocker_greet --testing` log kscreenlocker_greet: Greeter is starting up. kscreenlocker_greet: Greeter is running in testing mode kscreenlocker_greet: Testing mode enabled: true kscreenlocker_greet: [PAM worker kde-fingerprint] start: successfully started kscreenlocker_greet: [PAM worker kde-smartcard] start: successfully started kscreenlocker_greet: [PAM worker kde] start: successfully started Locked at 1778156568 kscreenlocker_greet: PamAuthenticators: starting authenticators kscreenlocker_greet: PamAuthenticators: state changing from PamAuthenticators::Idle to PamAuthenticators::Authenticating kscreenlocker_greet: [PAM worker kde] Authenticate: Starting authentication kscreenlocker_greet: [PAM worker kde-fingerprint] Authenticate: Starting authentication kscreenlocker_greet: [PAM worker kde-smartcard] Authenticate: Starting authentication kscreenlocker_greet: [PAM worker kde-fingerprint] Authenticate: Authentication done, result code: 28 (Module is unknown) kscreenlocker_greet: [PAM worker kde-smartcard] Authenticate: Authentication done, result code: 28 (Module is unknown) kscreenlocker_greet: PamAuthenticators: Availability changed for non-interactive authenticator kde-fingerprint true kscreenlocker_greet: PamAuthenticators: Availability changed for non-interactive authenticator kde-smartcard true kscreenlocker_greet: PamAuthenticators: Delay started on login failure for non-interactive authenticator kde-fingerprint duration: 2331494 kscreenlocker_greet: PamAuthenticators: Delay started on login failure for non-interactive authenticator kde-smartcard duration: 2134096 kscreenlocker_greet: PamAuthenticators: Availability changed for non-interactive authenticator kde-smartcard false kscreenlocker_greet: PamAuthenticators: Availability changed for non-interactive authenticator kde-smartcard false kscreenlocker_greet: PamAuthenticators: Availability changed for non-interactive authenticator kde-fingerprint false kscreenlocker_greet: PamAuthenticators: Availability changed for non-interactive authenticator kde-fingerprint false kscreenlocker_greet: [PAM worker kde] Message: Echo-off prompt: Password: kscreenlocker_greet: [PAM worker kde] Starting nested event loop to await response kscreenlocker_greet: PamAuthenticators: Secret prompt from interactive authenticator kde kscreenlocker_greet: PamAuthenticators: responding to interactive authenticator kscreenlocker_greet: [PAM worker kde] Received response, exiting nested event loop kscreenlocker_greet: PamAuthenticators: Interactive authenticator kde changed business kscreenlocker_greet: [PAM worker] Fail delay function was called, but authentication result was a success! kscreenlocker_greet: [PAM worker kde] Authenticate: Authentication done, result code: 0 (Success) kscreenlocker_greet: PamAuthenticators: Interactive authenticator kde changed business kscreenlocker_greet: PamAuthenticators: Success from interactive authenticator kde Unlocked ========= `faillock --user $USER` output cthulhu: When Type Source Valid ========= `/usr/lib/pam.d/kde` content auth include system-local-login account include system-local-login password include system-local-login session include system-local-login ========= Let me know if you need me to test anything else! 2514371 4 kdedev 2026-05-07 16:05:47 +0000 Thanks! That's helpful. The developers will need to take a closer look 2532044 5 nate 2026-07-15 20:32:35 +0000 Thanks. Looks like the same root cause as Bug 521900. *** This bug has been marked as a duplicate of bug 521900 *** 191787 2026-04-25 12:32:05 +0000 2026-04-25 12:32:05 +0000 kscreenlocker logs gathered using "journalctl -b 0 | grep -i kscreenlocker" kscreenlocker_logs.txt text/plain 785 hi QXByIDI1IDEwOjQ0OjUwIFJseWVoIGtzY3JlZW5sb2NrZXJfZ3JlZXRbMTk0MDZdOiBwYW1fdW5p eChrZGU6YXV0aCk6IHVuZXhwZWN0ZWQgcmVzcG9uc2UgZnJvbSBmYWlsZWQgY29udmVyc2F0aW9u IGZ1bmN0aW9uCkFwciAyNSAxMDo0NDo1MCBSbHllaCBrc2NyZWVubG9ja2VyX2dyZWV0WzE5NDA2 XTogcGFtX3VuaXgoa2RlOmF1dGgpOiBjb252ZXJzYXRpb24gZmFpbGVkCkFwciAyNSAxMDo0NDo1 MCBSbHllaCBrc2NyZWVubG9ja2VyX2dyZWV0WzE5NDA2XTogcGFtX3VuaXgoa2RlOmF1dGgpOiBh dXRoIGNvdWxkIG5vdCBpZGVudGlmeSBwYXNzd29yZCBmb3IgW2N0aHVsaHVdCkFwciAyNSAxMDo0 NTowMiBSbHllaCBrc2NyZWVubG9ja2VyX2dyZWV0WzE5NDA2XTogcGFtX3VuaXgoa2RlOmF1dGgp OiB1bmV4cGVjdGVkIHJlc3BvbnNlIGZyb20gZmFpbGVkIGNvbnZlcnNhdGlvbiBmdW5jdGlvbgpB cHIgMjUgMTA6NDU6MDIgUmx5ZWgga3NjcmVlbmxvY2tlcl9ncmVldFsxOTQwNl06IHBhbV91bml4 KGtkZTphdXRoKTogY29udmVyc2F0aW9uIGZhaWxlZApBcHIgMjUgMTA6NDU6MDIgUmx5ZWgga3Nj cmVlbmxvY2tlcl9ncmVldFsxOTQwNl06IHBhbV91bml4KGtkZTphdXRoKTogYXV0aCBjb3VsZCBu b3QgaWRlbnRpZnkgcGFzc3dvcmQgZm9yIFtjdGh1bGh1XQpBcHIgMjUgMTc6NTQ6MDggUmx5ZWgg a3NjcmVlbmxvY2tlcl9ncmVldFsxOTQwNl06IFtQQU0gd29ya2VyIGtkZV0gQXV0aGVudGljYXRp b24gYXR0ZW1wdCB0b28gc29vbi4gVGhpcyBzaG91bGRuJ3QgaGFwcGVuIQo=