CVE-2026-61915

Integer overflow in the index_urlfetch function in imap/index.c in Cyrus IMAP 2.3.19, 2.4.18, and 2.5.6 allows remote attackers to have unspecified impact via vectors related to urlfetch range checks and the start_octet variable.

The index_urlfetch function in Cyrus IMAP versions 2.3.x before 2.3.19, 2.4.x before 2.4.18, and 2.5.x before 2.5.4 allows remote attackers to obtain sensitive information or possibly have unspecified other impact via vectors related to the urlfetch range, which triggers an out-of-bounds heap read.

In the mboxlist_do_find function in Cyrus IMAP before version 3.0.4, an off-by-one error in prefix calculation for the LIST command led to the use of uninitialized memory. This may allow remote attackers to obtain sensitive information or cause a daemon crash.

In Cyrus IMAP before 3.12.4, there is a Sieve mailbox existence oracle. An authenticated user can install a Sieve script that probes whether another user's private mailbox exists, or reads the value of shared mailbox annotations, by observing which fileinto branch fires during LMTP delivery.

In Cyrus IMAP before 3.12.4, Mailbox/set let a sharee change a special-use role on shared mailboxes. An authenticated user with maySetKeywords on another user's mailbox could change that mailbox's specialuse annotation. This could allow the sharee to change the shared mailbox to perform the archived, snoozed, or other role, which might cause mail to be written to the shared mailbox, sharing more content than intended.

In Cyrus IMAP before 3.12.4, CalDAV/CardDAV multiget bypasses a per-href ACL. An authenticated DAV user with some shared access to another user's calendar or address book could read even unshared events or contacts by including the target hrefs in a calendar-multiget or addressbook-multiget REPORT.

In Cyrus IMAP before 3.12.4, a JMAP email-header blob ID can reference an out-of-bounds index. An authenticated user could attempt to download a crafted JMAP blob ID of the form H<emailid>-<index>, which could read past the end of the internal blob_headers array during download, exposing adjacent heap memory.

In Cyrus IMAP before 3.12.4, JMAP snooze bypasses the destination-mailbox ACL. An authenticated user with insert permissions on another user's snoozed mailbox could cause insertion of mail to that user's inbox, or any other of their mailboxes whose id was known to the user, despite having no insert permissions to the target mailbox.

In cyrus-imapd up to version 3.12.2, the LISTRIGHTS command was not restricted to users with admin access. An authenticated user could call LISTRIGHTS against any mailbox they could name and learn what principals had what access to it.

In cyrus-imapd up to version 3.12.2, a vulnerability was discovered involving heap exposure during parsing of nested MIME comments. An authenticated IMAP user can craft an email message containing an RFC 822 comment ending with a backslash, causing the server to read past the message's end in memory and return heap content.