Environment: Carbonio CE 26.6.0 (carbonio-appserver 4.5.1, appserver-conf 4.27.13, Ubuntu 24.04). Client: macOS 26.5 Contacts ().
Problem: A CardDAV PUT of a vCard whose PHOTO property carries no TYPE parameter fails with HTTP 500. Current macOS Contacts adds TYPE=JPEG for JPEG photos but omits the parameter entirely for PNG photos. Per RFC 2426 TYPE is optional, so the vCard is valid — but the server rejects it.
Impact is bigger than one contact. The client never gets a success, so it retries the same PUT every 30-60 minutes forever, and the failing upload aborts the sync session before the download step. The result is a mailbox that looks like "CardDAV is broken on macOS": new contacts created on other devices never reach the Mac. In our case the account had one contact with a PNG photo and the whole address book stopped syncing on macOS while iOS and Thunderbird worked fine. Recovering required removing and re-adding the account on the Mac, because the queued upload survives both editing the contact and toggling Contacts for the account.
Reproduce: PUT to /dav/<user>/Contacts/<uid>.vcf:
PHOTO;ENCODING=b;TYPE=JPEG:... is accepted.Server log (mailbox.log):
Cause and suggested fix — VCard.java line 340 calls .toUpperCase() on a value that is null when the parameter is absent. The very next lines already handle an empty suffix, so the guard looks like an oversight:
If a concrete subtype is needed, it can be detected from the decoded payload's magic bytes (\x89PNG, \xFF\xD8\xFF for JPEG).
I originally filed this on GitHub as <a id="base-ui-_r_2tjm_" class="text-accent hover:underline underline-offset-[1px] outline-none hide-focus-ring ring-focus rounded-r2" href=" removed link " target="_blank" rel="noopener noreferrer">zextras/carbonio-mailbox#1117 and it was closed automatically with a pointer to this forum, so I am reposting it here.