CVE-2023-23943: Nextcloud mail is an email app for the nextcloud home server platform

Routine

MEDIUM 5.0UPGRADE

CVE-2023-23943 is a medium-severity flaw (CVSS 5.0) affecting mail. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Nextcloud mail is an email app for the nextcloud home server platform. In affected versions the SMTP, IMAP and Sieve host fields allowed to scan for internal services and servers reachable from within the local network of the Nextcloud Server. It is recommended that the Nextcloud Maill app is upgraded to 1.15.0 or 2.2.2. The only known workaround for this issue is to completely disable the nextcloud mail app.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.0 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-918
Published	2023-02-06
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: nextcloud

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-02-06 21:15 UTCPublished CVE record published
2026-06-17 05:38 UTCUpdated Record last modified

nextcloud mail UPGRADE

Affected: < 1.15.0 · >= 2.2.0 and < 2.2.2

Fixed in: 1.15.0, 2.2.2

Safe to downgrade to: a release before 2.2.0

1. Check installed version

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

2. UPGRADE to 1.15.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mail

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 2.2.0 (Debian / Ubuntu)

apt-cache madison mail sudo apt install mail=<VERSION_BEFORE_2.2.0> sudo apt-mark hold mail

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

dnf --showduplicates list mail sudo dnf downgrade mail-<VERSION_BEFORE_2.2.0> sudo dnf versionlock add mail

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-2023-23943?

mail: upgrade to 1.15.0, 2.2.2. Exact commands for each OS are on this page.

Is CVE-2023-23943 being exploited?

CVE-2023-23943 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-2023-23943 affect?

CVE-2023-23943 affects mail. Severity is medium (CVSS 5.0). Nextcloud mail is an email app for the nextcloud home server platform. In affected versions the SMTP, IMAP and Sieve host fields allowed to scan for internal services and servers reachable from within the local network of the Nextcloud Serv

How urgent is CVE-2023-23943?

Priority 38/100. Public exploit reference

Software pages

Nextcloud vulnerabilities

Related CVEs

CVE-2025-66514 LOW 3.5 UPGRADE Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform
CVE-2024-52509 LOW 3.5 UPGRADE Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform
CVE-2024-52508 HIGH 8.2 UPGRADE Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform
CVE-2023-48307 LOW 3.5 UPGRADE Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform
CVE-2023-45660 MEDIUM 4.3 UPGRADE Nextcloud mail is an email app for the Nextcloud home server platform

References

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