CVE-2026-61909: An issue was discovered in Cyrus IMAP before 3.12.4

Routine

LOW 3.5UPGRADE

CVE-2026-61909 is a low-severity flaw (CVSS 3.5) affecting imap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	3.5 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 90%)
CISA exploited list	No
Weakness	CWE-420
Published	2026-09-09
Last modified	2026-09-16

Publisher (CNA): MITRE · Vendor: cyrus

Last updated 2026-09-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-09 20:18 UTCPublished CVE record published
2026-09-16 15:24 UTCUpdated Record last modified

cyrus imap UPGRADE

Affected: < 3.8.8 · >= 3.9.0 and < 3.10.4 · >= 3.11.0 and < 3.12.4

Fixed in: 3.8.8, 3.10.4, 3.12.4

Safe to downgrade to: a release before 3.9.0

1. Check installed version

apt-cache policy imap || rpm -q imap || imap --version

2. UPGRADE to 3.8.8 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade imap

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade imap

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.9.0 (Debian / Ubuntu)

apt-cache madison imap sudo apt install imap=<VERSION_BEFORE_3.9.0> sudo apt-mark hold imap

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list imap sudo dnf downgrade imap-<VERSION_BEFORE_3.9.0> sudo dnf versionlock add imap

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-61909?

imap: upgrade to 3.8.8, 3.10.4, 3.12.4. Exact commands for each OS are on this page.

Is CVE-2026-61909 being exploited?

CVE-2026-61909 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-61909 affect?

CVE-2026-61909 affects imap. Severity is low (CVSS 3.5). 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 b

How urgent is CVE-2026-61909?

Priority 15/100. No elevated risk signals yet.

Related CVEs

CVE-2026-61908 LOW 3.1 UPGRADE An issue was discovered in Cyrus IMAP before 3.12.4
CVE-2026-61910 LOW 3.5 UPGRADE An issue was discovered in Cyrus IMAP before 3.12.4
CVE-2026-61911 MEDIUM 4.3 UPGRADE An issue was discovered in Cyrus IMAP before 3.12.4
CVE-2026-61915 MEDIUM 4.2 UPGRADE An issue was discovered in Cyrus IMAP before 3.12.4

References

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