When trying to reset the password in such configuration a "System Error" occurs as below:

java.lang.UnsupportedOperationException: Cannot write to read-only UserManager [ldapRepository] java.lang.UnsupportedOperationException: Cannot write to read-only UserManager [ldapRepository]
at com.atlassian.user.impl.ReadOnlyUserManager.alterPassword(ReadOnlyUserManager.java:29)
at com.atlassian.user.impl.cache.CachingUserManager.alterPassword(CachingUserManager.java:138)
at com.atlassian.user.impl.delegation.DelegatingListUserManager.alterPassword(DelegatingListUserManager.java:127)
at bucket.user.DefaultUserAccessor.alterPassword(DefaultUserAccessor.java:695)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.springframework.aop.framework.AopProxyUtils.invokeJoinpointUsingReflection(AopProxyUtils.java:61)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:149)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:116)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:56)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:138)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:152)
at $Proxy11.alterPassword(Unknown Source)
at com.atlassian.confluence.user.actions.ForgotUserPasswordAction.execute(ForgotUserPasswordAction.java:49)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:168)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.opensymphony.xwork.interceptor.DefaultWorkflowInterceptor.intercept(DefaultWorkflowInterceptor.java:55)
at com.atlassian.confluence.core.ConfluenceWorkflowInterceptor.intercept(ConfluenceWorkflowInterceptor.java:39)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
...