An issue was discovered 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.
CVSS Score
3.1
EPSS Score
0.002
Published
2026-09-09
An issue was discovered 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.
CVSS Score
3.5
EPSS Score
0.002
Published
2026-09-09
An issue was discovered 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 mail to be written to the shared mailbox, sharing more content than intended. (This is likely to be an unusual situation, made more unusual because if the target already has an non-shared mailbox with that role, role duplication suppression will prevent the update.)
CVSS Score
3.5
EPSS Score
0.002
Published
2026-09-09
An issue was discovered in Cyrus IMAP before 3.12.4. There is a Sieve mailbox existence oracle. An authenticated user could install a Sieve script that probed whether another user's private mailbox existed, or read the value of shared mailbox annotations, by observing which fileinto branch fired during LMTP delivery.
CVSS Score
4.3
EPSS Score
0.002
Published
2026-09-09
An issue was discovered in Cyrus IMAP before 3.12.4. There is a VPATCH BYPARAM double-free. An authenticated calendar user could crash a Cyrus CalDAV worker with a PATCH containing PATCH-ACTION="BYPARAM@..." against a resource with two or more properties of the matched kind. The memory holding the selector would be freed once on each iteration over the properties.
CVSS Score
4.2
EPSS Score
0.002
Published
2026-09-09
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.
CVSS Score
7.5
EPSS Score
0.031
Published
2021-09-01
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.
CVSS Score
4.3
EPSS Score
0.017
Published
2021-05-10
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.
CVSS Score
6.5
EPSS Score
0.017
Published
2019-12-16
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.
CVSS Score
9.8
EPSS Score
0.024
Published
2019-11-15
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.
CVSS Score
9.8
EPSS Score
0.076
Published
2019-06-03
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