Trust anchor for certification path not found.

[EddyLnx]

Hi,

Since recent update on Sept. 3, 2025, I can no longer access my work calendar because I get the following error

java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.

Unfortunately I have no clue on how certificates work on android devices. I contacted the server admin where the calendar is available and they say that everything is fine on their side. I can access the calendar from thunderbird on my laptop.

Since the problem started just after the app was updated, I wonder if it could be a bug.

I don't know if this is useful at all but I can download the ics file using firefox for android on the same phone without any problem.

My version of icsx5 : 2.4.0 from GooglePlay
My version of android : 13

Any idea what I could do ?

Thanks anyway,

[EddyLnx]

I did a little bit of research on the subject.

The server where the ics file is stored is certified by GEANT TLS RSA 1 which is itself certified by HARICA TLS RSA Root CA 2021 but on my phone there is only HARICA TLS RSA Root CA 2015.

I installed HARICA TLS RSA Root CA 2021 as a user certificate and now icsx5 works again for me.

The conclusion seems to be that the app failed to download my ics file because I didn't have the right certificate (which by the way is a 7 year old phone for which Samsung does not provide updates anymore). What I completely fail to understand is why the app failed right after it was updated to version 2.4.0. : certificates were the same on my phone one week ago and previous version of icsx didn't complain.

As I said before, I do not understand how the certificate chain works on android so if anyone can enlighten me on why things changed suddenly, I'd be very happy indeed.

[sunkup]

Hey, thanks for reporting. Probably the same as #693

[sunkup]

Tracked in #692