Vulnerabilities

CVE-2026-61915 is a double-free (CWE-415) in the VPATCH BYPARAM handling of Cyrus IMAP's CalDAV support, fixed in version 3.12.4. An authenticated calendar user triggers it by sending a PATCH request with PATCH-ACTION="BYPARAM@..." against a resource containing two or more properties of the matched kind, which frees the memory holding the selector once on each iteration over the properties. The result is a crash of the CalDAV worker process — a denial-of-service condition with high availability impact, no confidentiality impact, and only low integrity impact per the CVSS score of 7.1. Any Cyrus IMAP deployment before 3.12.4 with the CalDAV/calendar component enabled and reachable by authenticated users is affected. There is currently no public proof-of-concept, no CISA KEV listing, and EPSS assigns only a 0.2% probability of exploitation within 30 days.

Do: Upgrade Cyrus IMAP to 3.12.4 or later. Where immediate upgrade is not possible, restrict CalDAV access to trusted authenticated accounts, monitor CalDAV worker (httpd) processes for repeated crashes or restarts, and consider blocking calendar PATCH requests carrying PATCH-ACTION="BYPARAM@..." at a fronting proxy or disabling the calendar service until patched.

Cyrus IMAP before 3.8.3 and 3.10.x before 3.10.0-rc1 allows authenticated attackers to cause unbounded memory allocation by sending many LITERALs in a single command.

In Cyrus SASL 2.1.17 through 2.1.27 before 2.1.28, plugins/sql.c does not escape the password for a SQL INSERT or UPDATE statement.

Cyrus IMAP before 3.4.2 allows remote attackers to cause a denial of service (multiple-minute daemon hang) via input that is mishandled during hash-table interaction. Because there are many insertions into a single bucket, strcmp becomes slow. This is fixed in 3.4.2, 3.2.8, and 3.0.16.

Cyrus IMAP before 3.2.7, and 3.3.x and 3.4.x before 3.4.1, allows remote authenticated users to bypass intended access restrictions on server annotations and consequently cause replication to stall.

cyrus-sasl (aka Cyrus SASL) 2.1.27 has an out-of-bounds write leading to unauthenticated remote denial-of-service in OpenLDAP via a malformed LDAP packet. The OpenLDAP crash is ultimately caused by an off-by-one error in _sasl_add_string in common.c in cyrus-sasl.

An issue was discovered in Cyrus IMAP before 2.5.15, 3.0.x before 3.0.13, and 3.1.x through 3.1.8. If sieve script uploading is allowed (3.x) or certain non-default sieve options are enabled (2.x), a user with a mail account on the service can use a sieve script containing a fileinto directive to create any mailbox with administrator privileges, because of folder mishandling in autosieve_createfolder() in imap/lmtp_sieve.c.

Cyrus IMAP 2.5.x before 2.5.14 and 3.x before 3.0.12 allows privilege escalation because an HTTP request may be interpreted in the authentication context of an unrelated previous request that arrived over the same connection.

The CalDAV feature in httpd in Cyrus IMAP 2.5.x through 2.5.12 and 3.0.x through 3.0.9 allows remote attackers to execute arbitrary code via a crafted HTTP PUT operation for an event with a long iCalendar property name.

In the mboxlist_do_find function in imap/mboxlist.c in Cyrus IMAP before 3.0.4, an off-by-one error in prefix calculation for the LIST command caused use of uninitialized memory, which might allow remote attackers to obtain sensitive information or cause a denial of service (daemon crash) via a 'LIST "" "Other Users"' command.

Cyrus IMAP before 3.0.3 allows remote authenticated users to write to arbitrary files via a crafted (1) SYNCAPPLY, (2) SYNCGET or (3) SYNCRESTORE command.