FreeRADIUS v.3.2.8 - preprocess: ERROR: regex evaluation failed with code (-51): NULL argument passed with non-zero length

23 Jan 2026

      Hi everyone,
I was using FreeRADIUS version 3.2.6 for x86_64-redhat-linux-gnu (Red Hat
Enterprise Linux release 9.4),
with Oracle Database 19 as the backend.

I encountered some memory issues, so I upgraded to version 3.2.8,

but the configuration in the preprocessing hints file, which was working
perfectly with version 3.2.6, no longer works.

 DEFAULT Called-Station-Id =~ ".*491113$", User-Name =~
"^([^@]*)@((?i)libero.*)", Strip-User-Name = Yes

        Hint = "Access",
        Stripped-User-Name = "%{1}",
        Realm = "%{2}"

1) Version 3.2.6
echo "User-Name=brignani@libero.it,User-Password=******,Calling-Station-Id=_TEST-SDWAN-A0001,Called-Station-Id=755491113"
| radclient -x 10.10.0.221:1812 auth "pippo"
Sent Access-Request Id 3 from 0.0.0.0:55865 to xx.xx.x.xxx:1812 length 106
        Message-Authenticator = 0x
        User-Name = "brignani@libero.it"
        User-Password = "******"
        Calling-Station-Id = "_TEST-SDWAN-A0001"
        Called-Station-Id = "755491113"
        Cleartext-Password = "******"
Received Access-Accept Id 3 from xx.xx.x.xxx:1812 to xx.xx.x.xxx:55865
length 138
        Service-Type = Framed-User
        Framed-Protocol = PPP
        Class =
0x415f313736393030393530385f4e413d554e4b4e4f574e5f313030303232375f323235373832365f313030303038385f313030303030305f313030305f595f4e5f305f313030303330385f305f4141413a7261643031
        Message-Authenticator = 0xa0a3af25b5ebba0db2ad8f374aa7f5b4

Wed Jan 21 16:31:48 2026 : Debug: (0)           EXPAND %{debug:3}
Wed Jan 21 16:31:48 2026 : Debug: (0)              --> 0
Wed Jan 21 16:31:48 2026 : Debug: (0)         } # update control = noop
Wed Jan 21 16:31:48 2026 : Debug: (0)       } # if (true == "true")  = noop
Wed Jan 21 16:31:48 2026 : Debug: (0)     } # policy debug-rule = noop
Wed Jan 21 16:31:48 2026 : Debug: (0)     modsingle[authorize]: calling
preprocess (rlm_preprocess)
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND ^([^@]*)@((?i)
greenlake.it)$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> ^([^@]*)@((?i)
greenlake.it)$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND ^([^@]*)@((?i)
noise.it)$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> ^([^@]*)@((?i)
noise.it)$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*0000$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*0000$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*0020$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*2990$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*2990$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*1010$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*1010$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND .*491113$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> .*491113$
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND
^([^@]*)@((?i)libero.*)
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    -->
^([^@]*)@((?i)libero.*)
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: hints: Matched DEFAULT at
138
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND %{1}
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> brignani
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess: EXPAND %{2}
Wed Jan 21 16:31:48 2026 : Debug: (0) preprocess:    --> libero.it
Wed Jan 21 16:31:48 2026 : Debug: (0)     modsingle[authorize]: returned
from preprocess (rlm_preprocess)
Wed Jan 21 16:31:48 2026 : Debug: (0)     [preprocess] = ok
Wed Jan 21 16:31:48 2026 : Debug: (0)     if (!&request:User-Name) {
Wed Jan 21 16:31:48 2026 : Debug: (0)     if (!&request:User-Name)  -> FALSE
Wed Jan 21 16:31:48 2026 : Debug: (0)     policy nas-info {
Wed Jan 21 16:31:48 2026 : Debug: (0)       update control {
Wed Jan 21 16:31:48 2026 : Debug: (0)       } # update control = noop
Wed Jan 21 16:31:48 2026 : Debug: (0)       modsingle[authorize]: calling
cache-nas (rlm_cache)
Wed Jan 21 16:31:48 2026 : Debug: (0) cache-nas: EXPAND %{NAS-IP-Address}
Wed Jan 21 16:31:48 2026 : Debug: (0) cache-nas:    --> xx.xx.x.xxx
Wed Jan 21 16:31:48 2026 : Debug: (0) cache-nas: Mutex acquired
Wed Jan 21 16:31:48 2026 : Debug: (0) cache-nas: No cache entry found for
"xx.xx.x.xxx"
Wed Jan 21 16:31:48 2026 : Debug: (0) cache-nas: Mutex released
Wed Jan 21 16:31:48 2026 : Debug: (0)       modsingle[authorize]: returned
from cache-nas (rlm_cache)
Wed Jan 21 16:31:48 2026 : Debug: (0)       [cache-nas] = notfound
Wed Jan 21 16:31:48 2026 : Debug: (0)       if (notfound) {
Wed Jan 21 16:31:48 2026 : Debug: (0)       if (notfound)  -> TRUE
Wed Jan 21 16:31:48 2026 : Debug: (0)       if (notfound)  {
Wed Jan 21 16:31:48 2026 : Debug: (0)         update control {
Wed Jan 21 16:31:48 2026 : Debug: (0)           EXPAND
%{%{Stripped-User-Name}:-%{%{User-Name}:-DEFAULT}}
Wed Jan 21 16:31:48 2026 : Debug: (0)              --> brignani
Wed Jan 21 16:31:48 2026 : Debug: (0)           SQL-User-Name set to
'brignani'

2) Version 3.2.8
[root@glaaarad01 ~]# echo
"User-Name=brignani@libero.it,User-Password=******,Calling-Station-Id=_TEST-SDWAN-A0001,Called-Station-Id=755491113"
| radclient -x 10.10.1.217:1812 auth "pippo"
Sent Access-Request Id 9 from 0.0.0.0:48083 to xx.xx.x.xxx:1812 length 106
        User-Name = "brignani@libero.it"
        User-Password = "******"
        Calling-Station-Id = "_TEST-SDWAN-A0001"
        Called-Station-Id = "755491113"
        Cleartext-Password = "******"
Received Access-Reject Id 9 from xx.xx.x.xxx:1812 to xx.xx.x.xxx:48083
length 38
        Message-Authenticator = 0xbca819113f66bc3aa5b2f79c3aef6ecc
(0) -: Expected Access-Accept got Access-Reject

Wed Jan 21 16:36:50 2026 : Debug: (0)           EXPAND %{debug:3}
Wed Jan 21 16:36:50 2026 : Debug: (0)              --> 0
Wed Jan 21 16:36:50 2026 : Debug: (0)         } # update control = noop
Wed Jan 21 16:36:50 2026 : Debug: (0)       } # if (true == "true")  = noop
Wed Jan 21 16:36:50 2026 : Debug: (0)     } # policy debug-rule = noop
Wed Jan 21 16:36:50 2026 : Debug: (0)     modsingle[authorize]: calling
preprocess (rlm_preprocess)
Wed Jan 21 16:36:50 2026 : ERROR: (0) preprocess: ERROR: regex evaluation
failed with code (-51): NULL argument passed with non-zero length
Wed Jan 21 16:36:50 2026 : ERROR: (0) preprocess: ERROR: regex evaluation
failed with code (-51): NULL argument passed with non-zero length
Wed Jan 21 16:36:50 2026 : ERROR: (0) preprocess: ERROR: regex evaluation
failed with code (-51): NULL argument passed with non-zero length
Wed Jan 21 16:36:50 2026 : ERROR: (0) preprocess: ERROR: regex evaluation
failed with code (-51): NULL argument passed with non-zero length
Wed Jan 21 16:36:50 2026 : ERROR: (0) preprocess: ERROR: regex evaluation
failed with code (-51): NULL argument passed with non-zero length
Wed Jan 21 16:36:50 2026 : ERROR: (0) preprocess: ERROR: regex evaluation
failed with code (-51): NULL argument passed with non-zero length
...
Wed Jan 21 16:36:50 2026 : Debug: (0)     modsingle[authorize]: returned
from preprocess (rlm_preprocess)
Wed Jan 21 16:36:50 2026 : Debug: (0)     [preprocess] = ok
Wed Jan 21 16:36:50 2026 : Debug: (0)     if (!&request:User-Name) {
Wed Jan 21 16:36:50 2026 : Debug: (0)     if (!&request:User-Name)  -> FALSE
Wed Jan 21 16:36:50 2026 : Debug: (0)     policy nas-info {
Wed Jan 21 16:36:50 2026 : Debug: (0)       update control {
Wed Jan 21 16:36:50 2026 : Debug: (0)       } # update control = noop
Wed Jan 21 16:36:50 2026 : Debug: (0)       modsingle[authorize]: calling
cache-nas (rlm_cache)
Wed Jan 21 16:36:50 2026 : Debug: (0) cache-nas: EXPAND %{NAS-IP-Address}
Wed Jan 21 16:36:50 2026 : Debug: (0) cache-nas:    --> xx.xx.x.xxx
Wed Jan 21 16:36:50 2026 : Debug: (0) cache-nas: Mutex acquired
Wed Jan 21 16:36:50 2026 : Debug: (0) cache-nas: No cache entry found for
"xx.xx.x.xxx"
Wed Jan 21 16:36:50 2026 : Debug: (0) cache-nas: Mutex released
Wed Jan 21 16:36:50 2026 : Debug: (0)       modsingle[authorize]: returned
from cache-nas (rlm_cache)
Wed Jan 21 16:36:50 2026 : Debug: (0)       [cache-nas] = notfound
Wed Jan 21 16:36:50 2026 : Debug: (0)       if (notfound) {
Wed Jan 21 16:36:50 2026 : Debug: (0)       if (notfound)  -> TRUE
Wed Jan 21 16:36:50 2026 : Debug: (0)       if (notfound)  {
Wed Jan 21 16:36:50 2026 : Debug: (0)         update control {
Wed Jan 21 16:36:50 2026 : Debug: (0)           EXPAND
%{%{Stripped-User-Name}:-%{%{User-Name}:-DEFAULT}}
Wed Jan 21 16:36:50 2026 : Debug: (0)              --> brignani@libero.it

Kind regards,
Andrea

FreeRADIUS v.3.2.8 - preprocess: ERROR: regex evaluation failed with code (-51): NULL argument passed with non-zero length

Ciummi